I've discovered that the problem only occurs on .aac files, which used to work on the old music player. This is a bit of a pity for me because my whole library is in .aac, so a fix would be very welcome.
I've update to the latest version (2.6.8) and now my music player stops playing music after a while, it usually does not finish the song. I've made a logcat which is attached, and there it seems to be a "media error -1400", a part of the log is given below: