It's very unlikely to be disk problems (fsck is run automatically every few syncs).

As Tony pointed out, Mike introduced file validity code to prevent the player hanging on bad files - a condition that was rather hard to escape from. The code searches for a sychronisation frame and then checks for another sync at the appropriate distance further down the file. If it doesn't find these it throws out the MP3 because there's something wrong with it.

It's possible that the "something wrong" could be certain ID3V2 tags, for which support has not yet been implemented.

I don't think there's anything wrong with the validation code - I've personally listened to at least a couple of hundred tracks on a number of players since Beta10A and none of them have been rejected. As far as I'm aware nobody else has reported a problem.

Rob