Thanks,
I updated the driver, and that seems to have done something. Did crash once more, same sort of bug report but the number was different if I recall correctly: #6242. Later on instead of crashing it only got into "lag mode" with and index of around 0.1, where only restart of mpc or svp got it working properly again.
However I think I found what is causing the problems; I had been playing the files directly from the compressed .rar archive, which was also on a network drive. Unpacked the files instead and have not had any issues since.
So maybe it's still some sort of bug, but the workaround is simple; just don't play unzipped files directly.