Here is the log of DownloadMaster:

1 26.08.2014 18:23:29 Download state changed to Downloading
2 26.08.2014 18:23:29 Start new section [1]
3 26.08.2014 18:23:29 Start connection to [url=http://www.youtube.com:80]www.youtube.com:80[/url] [1]
4 26.08.2014 18:23:29 Connecting to [url=http://www.youtube.com:80]www.youtube.com:80[/url] [1]
5 26.08.2014 18:23:29 Connected [1]
6 26.08.2014 18:23:29 GET /watch?v=u5KQQWlIgGc&noredirect=1 HTTP/1.0
                      User-Agent: Mozilla/5.0 (Windows NT 6.1; Trident/7.0; rv:11.0) like Gecko
                      Cookie: VISITOR_INFO1_LIVE=ao3h9MdkQS8; PREF=f1=50000000&fv=0.0.0&f5=30
                      Accept: */*
                      Referer: [url]http://www.youtube.com/[/url]
                      Pragma: no-cache
                      Cache-Control: no-cache
                      Host: [url=http://www.youtube.com]www.youtube.com[/url]
7 26.08.2014 18:23:29 HTTP/1.0 301 Moved Permanently
                      Date: Tue, 26 Aug 2014 15:23:30 GMT
                      Server: gwiseguy/2.0
                      Expires: Tue, 27 Apr 1971 19:44:06 EST
                      Content-Length: 0
                      Content-Type: text/html; charset=utf-8
                      Cache-Control: no-cache
                      X-Content-Type-Options: nosniff
                      Set-Cookie: YSC=tD5oc1CXdWM; path=/; domain=.youtube.com; httponly
                      Location: [url]https://www.youtube.com/watch?v=u5KQQWlIgGc&noredirect=1[/url]
                      X-XSS-Protection: 1; mode=block; report=https://www.google.com/appserve/security-bugs/log/youtube
                      P3P: CP="This is not a P3P policy! See [url]http://support.google.com/accounts/bin/answer.py?answer=151657&hl=en[/url] for more info."
                      X-Frame-Options: SAMEORIGIN
                      Alternate-Protocol: 80:quic
8 26.08.2014 18:23:29 Restart download. Server reply code: 301
9 26.08.2014 18:23:29 Closing socket [1]
10 26.08.2014 18:23:29 Socket disconnected [1]
11 26.08.2014 18:23:29 Start delete section [1]
12 26.08.2014 18:23:30 Section deleted [1]
13 26.08.2014 18:23:30 Start new section [1]
14 26.08.2014 18:23:30 Start connection to [url=http://www.youtube.com:443]www.youtube.com:443[/url] [1]
15 26.08.2014 18:23:30 Connecting to [url=http://www.youtube.com:443]www.youtube.com:443[/url] [1]
16 26.08.2014 18:23:30 Certificate is correct
17 26.08.2014 18:23:30 Version: 3
                       Issuer: Equifax
                       - country: US
                       - organization unit: Equifax Secure Certificate Authority
                       Subject: GeoTrust Global CA
                       Validity period: 21.05.2002 04:00:00 - 21.08.2018 04:00:00
18 26.08.2014 18:23:30 Certificate is correct
19 26.08.2014 18:23:30 Version: 3
                       Issuer: GeoTrust Inc.
                       - country: US
                       - common name: GeoTrust Global CA
                       Subject: Google Internet Authority G2
                       Validity period: 05.04.2013 15:15:55 - 04.04.2015 15:15:55
20 26.08.2014 18:23:30 Certificate is correct
21 26.08.2014 18:23:30 Version: 3
                       Issuer: Google Inc
                       - country: US
                       - common name: Google Internet Authority G2
                       Subject: *.google.com
                       Validity period: 30.07.2014 11:42:15 - 28.10.2014
22 26.08.2014 18:23:31 Connected [1]
23 26.08.2014 18:23:31 GET /watch?v=u5KQQWlIgGc&noredirect=1 HTTP/1.0
                       User-Agent: Mozilla/5.0 (Windows NT 6.1; Trident/7.0; rv:11.0) like Gecko
                       Cookie: VISITOR_INFO1_LIVE=ao3h9MdkQS8; PREF=f1=50000000&fv=0.0.0&f5=30; YSC=tD5oc1CXdWM
                       Accept: */*
                       Referer: [url]http://www.youtube.com/[/url]
                       Pragma: no-cache
                       Cache-Control: no-cache
                       Host: [url=http://www.youtube.com]www.youtube.com[/url]
24 26.08.2014 18:23:31 HTTP/1.0 200 OK
                       Date: Tue, 26 Aug 2014 15:23:32 GMT
                       Server: gwiseguy/2.0
                       Cache-Control: no-cache
                       Expires: Tue, 27 Apr 1971 19:44:06 EST
                       Content-Type: text/html; charset=utf-8
                       X-Content-Type-Options: nosniff
                       X-Frame-Options: SAMEORIGIN
                       X-XSS-Protection: 1; mode=block; report=https://www.google.com/appserve/security-bugs/log/youtube
25 26.08.2014 18:23:31 Socket disconnected [1]
26 26.08.2014 18:23:31 Section complete [1]
27 26.08.2014 18:23:31 Start delete section [1]
28 26.08.2014 18:23:31 Section deleted [1]
29 26.08.2014 18:23:31 Download state changed to Downloaded
30 26.08.2014 18:23:31 Download state changed to Downloading
31 26.08.2014 18:23:32 Start new section [1]
32 26.08.2014 18:23:32 Start connection to r3---sn-bpb5oxu-3c2l.googlevideo.com:443 [1]
33 26.08.2014 18:23:32 Connecting to r3---sn-bpb5oxu-3c2l.googlevideo.com:443 [1]
34 26.08.2014 18:23:32 Certificate is correct
35 26.08.2014 18:23:32 Version: 3
                       Issuer: Equifax
                       - country: US
                       - organization unit: Equifax Secure Certificate Authority
                       Subject: GeoTrust Global CA
                       Validity period: 21.05.2002 04:00:00 - 21.08.2018 04:00:00
36 26.08.2014 18:23:32 Certificate is correct
37 26.08.2014 18:23:32 Version: 3
                       Issuer: GeoTrust Inc.
                       - country: US
                       - common name: GeoTrust Global CA
                       Subject: Google Internet Authority G2
                       Validity period: 05.04.2013 15:15:55 - 04.04.2015 15:15:55
38 26.08.2014 18:23:32 Certificate is correct
39 26.08.2014 18:23:32 Version: 3
                       Issuer: Google Inc
                       - country: US
                       - common name: Google Internet Authority G2
                       Subject: *.googlevideo.com
                       Validity period: 15.04.2014 09:55:31 - 04.04.2015 15:15:55
40 26.08.2014 18:23:32 Connected [1]
41 26.08.2014 18:23:32 GET /videoplayback?id=o-AKXFmUKK7yV4F8QUpnYbLAy5g5U-VJhDETHVnZNRpnnS&mm=31&key=yt5&expire=1409088212&ip=93.188.36.151&ms=au&requiressl=yes&initcwndbps=5045000&ipbits=0&mv=m&sparams=id%2Cinitcwndbps%2Cip%2Cipbits%2Citag%2Cmm%2Cms%2Cmv%2Cratebypass%2Crequiressl%2Csource%2Cupn%2Cexpire&fexp=901064%2C902408%2C915514%2C927622%2C930817%2C931983%2C932317%2C932625%2C934024%2C934030%2C936210%2C938648%2C946022%2C948518&signature=D3C8B00E2DEB69100D181DE403740DF5303F18BB.570B4D6AC0C08A4D0AE3F8AC6356A77697424260&ratebypass=yes&sver=3&mt=1409066483&upn=YZrXcvuSwHw&itag=22&source=youtube&fallback_host=tc.v15.cache4.googlevideo.com&type=video/mp4;+codecs="avc1.64001F,+mp4a.40.2"&quality=hd720& HTTP/1.1
                       User-Agent: Mozilla/5.0 (Windows NT 6.1; Trident/7.0; rv:11.0) like Gecko
                       Cookie: VISITOR_INFO1_LIVE=ao3h9MdkQS8; PREF=f1=50000000&fv=0.0.0&f5=30; YSC=tD5oc1CXdWM
                       Accept: */*
                       Referer: [url]http://www.youtube.com/watch?v=u5KQQWlIgGc&noredirect=1[/url]
                       Cache-Control: no-cache
                       Host: r3---sn-bpb5oxu-3c2l.googlevideo.com
42 26.08.2014 18:23:32 HTTP/1.1 200 OK
                       Last-Modified: Sun, 17 Aug 2014 01:52:44 GMT
                       Content-Type: video/mp4
                       Date: Tue, 26 Aug 2014 15:23:33 GMT
                       Expires: Tue, 26 Aug 2014 15:23:33 GMT
                       Cache-Control: private, max-age=21299
                       Accept-Ranges: bytes
                       Content-Length: 24938864
                       Connection: close
                       Alternate-Protocol: 443:quic
                       X-Content-Type-Options: nosniff
                       Server: gvs 1.0
43 26.08.2014 18:23:34 Download state changed to Pausing
44 26.08.2014 18:23:34 Closing socket [1]
45 26.08.2014 18:23:34 Start delete section [1]
46 26.08.2014 18:23:34 Socket disconnected [1]
47 26.08.2014 18:23:35 Section deleted [1]
48 26.08.2014 18:23:35 Download state changed to Pause

deleted

This issue is not unique to SVPtube. E.g. https://productforums.google.com/forum/ … kn-VbYOvMo
https://www.google.com/search?q=pref%3Df1%3D50000000

Dear, Chainik, is it possible to add cookies PREF=f1=50000000; s_gl=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx== to the GET request, that SVPtube sends to Youtube server?

And now, ta-da!!! SVPtube again began to work!!!

GET /watch?v=u5KQQWlIgGc&gl=US&hl=en&has_verified=1 HTTP/1.1..User-Agent: SVPtube..Cookie: VISITOR_INFO1_LIVE=xxxxxxxxxxx; YSC=xxxxxxxxxxx; PREF=f1=50000000; s_gl=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx==..Connection: Keep-Alive..Accept-Encoding: gzip..Accept-Language: ru-RU,en,*..Host: www.youtube.com....

HTTP/1.1 200 OK..Date: Mon, 25 Aug 2014 19:27:51 GMT..Server: gwiseguy/2.0..P3P: CP="This is not a P3P policy! See http://support.google.com/accounts/bin/ … &hl=en for more info."..X-Content-Type-Options: nosniff..X-Frame-Options: SAMEORIGIN..Set-Cookie: s_gl=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx==; path=/; domain=.youtube.com..Expires: Tue, 27 Apr 1971 19:44:06 EST..Content-Type: text/html; charset=utf-8..Cache-Control: no-cache..X-XSS-Protection: 1; mode=block; report=https://www.google.com/appserve/security-bugs/log/youtube..Alternate-Protocol: 80:quic..Transfer-Encoding: chunked....a98..<!DOCTYPE html><html lang="ru" data-cast-api-enabled="true"><head><script>var ytcsi = {gt: function(n) {n = (n || '') + 'data_';return ytcsi[n] || (ytcsi[n] = {tick: {},span: {},info: {}});},tick: function(l, t, n) {ytcsi.gt(n).tick[l] = t || +new Date();},span: function(l, s, n) {ytcsi.gt(n).span[l] = (typeof s == 'number') ? s :+new Date() - ytcsi.data_.tick[l];},info: function(k, v, n) {ytcsi.gt(n).info[k] = v;}};(function(w, d) {ytcsi.perf = w.performance || w.mozPerformance ||w.msPerformance || w.webkitPerformance;ytcsi.tick('_start', ytcsi.perf ? ytcsi.perf.timing.responseStart : null);var isPrerender = (d.visibilityState || d.webkitVisibilityState) == 'prerender';var vName = d.webkitVisibilityState ? 'webkitvisibilitychange' : 'visibilitychange';if (isPrerender) {ytcsi.info('prerender', 1);var startTick = function() {y

Chainik
Yes, Livestreamer only allows to choose maximum 720p quality.
But, FlashGot in Firefox and DownloadMaster are functioning yet, e.g. I can download DASH streames.

Yeah, in fact this is the case. Maybe is it possible to receive links under such circumstances?
By the way, today I obtain the opportunity to select the video quality 1080p in a browser, which was previously disappeared.

PS. I also tried "Livestreamer" http://livestreamer.readthedocs.org/en/latest/.

c:\Program Files\Livestreamer>livestreamer https://www.youtube.com/watch?v=u5KQQWlIgGc

[cli][info] Found matching plugin youtube for URL https://www.youtube.com/watch?v=u5KQQWlIgGc
Available streams: 144p (worst), 240p, 360p, 720p (best)

c:\Program Files\Livestreamer>

As you can see, here I can choose only 720p. But in a browser also 1080p. Something strange.

Update. Livestreamer also stopped functioning.
Update2. Sorry, on the other video Livestreamer is working.

Finally, I decided thoroughly to dig out why SVPtube does not work.
And here are the results:

Out from SVPtube to Youtube "GET /watch?v=u5KQQWlIgGc&gl=US&hl=en&has_verified=1 HTTP/1.1..User-Agent: SVPtube..Cookie: VISITOR_INFO1_LIVE=xxxxxx; YSC=_xxxxxxxx..Connection: Keep-Alive..Accept-Encoding: gzip..Accept-Language: ru-RU,en,*..Host: www.youtube.com"

In to SVPtube from Youtube "HTTP/1.1 301 Moved Permanently..Date: Mon, 25 Aug 2014 13:14:20 GMT..Server: gwiseguy/2.0..X-Content-Type-Options: nosniff..Content-Length: 0..Location: https://www.youtube.com/watch?v=u5KQQWl … ..Expires: Tue, 27 Apr 1971 19:44:06 EST..Content-Type: text/html; charset=utf-8..Cache-Control: no-cache..X-XSS-Protection: 1; mode=block; report=https://www.google.com/appserve/security-bugs/log/youtube..X-Frame-Options: SAMEORIGIN..Alternate-Protocol: 80:quic"

My sequence of actions:
1. Booting PC
2. Opening a browser (e.g. Firefox)
3. Opening any page with embedded YT video
4. Right clicking on any embedded video and choosing "Copy URL"
5. Oops, nothing happens...
6. Closing SVPtube (right click -> Exit)
7. Opening any embedded YT video in a browser, playing it and closing YT page
8. Launching SVPtube
9. Right clicking on any other embedded YT video and coping its URL
10. Oops again, nothing...
11. Closing SVPube (right click -> Exit)
12. Coping to clipboard anything but not a link to YT video
13. Restarting SVPtube
14. Coping URL of any YT video
15. Ta-da!!! It's a mirracle!!! It's working!!! smile

Let's try again:
1. Boot your PC
2. Open a browser (e.g. Firefox, don't copy to clipboard any URL of YT video)
3. Open any YT video in YT page, play it and close YT page
4. Open any page with embedded YT video
5. Right click on any embedded video and choose "Copy URL"
6. You'll see Jesus, oh, sorry, only working SVPtube smile

Chainik
I just noticed, that you've said "This test version is logging only "encrypted" videos " That's why I could not obtain logs, because I didn't watch "encrypted" videos. SVPtube hangs on every YT video after booting PC. E.g., 
http://habrahabr.ru/company/mailru/blog/234271/ But after playing at least one any video in a browser, SVPtube is working well.

I definitely found out the core of the problem - until at least one Youtube video would not be played in a browser, SVPtube shows me "Getting info for video 'la-la-la' "
Dear SVP developer, Chainik, how could I obtain full logs because the special test build does not collect information when I'm getting '"Getting info for video 'la-la-la' ",  I'm finding "YT-xxxxxx.log"  in %TEMP% only after the "good start".

Unfortunately, the problem came back. And I have to do the same rite as piquadrat does to force SVPtube to work properly.

Maybe it is a miracle or something else, but during last 2 days SVPtube works fine. I did not do anything with my system.

Chainik
I observe this issue just after booting PC, but after playing at least one Youtube video in a browser and subsequent forced shutdown SVPtube by Task Manager (not through the menu of SVPtube) followed by its restart, the problem disappears.

I have the same issue as described in this topic.
Logs: