I have had the same issue, and recently posted this
elsewhere:
My zune did the same thing twice this morning. Called Zune support, and learned that the support reps got a memo about this today. They are watching the issue and trying to diagnose it. Their belief — supported by my usage — is that this problem occurs only with certain types of encoding or DRM or errors in files. So it’s not a hardware problem — returning the device won’t help. It’s a firmware problem or a problem with a particular media file or type of file.
The most useful thing for us to do to help them fix this is to figure out what’s common about the files that cause the reset.
Most important: Does the same song always reset the zune? If so, we can narrow our focus to what it is about that song.
Of course, it could also be an intermittent error with a particular type of song, which will be trickier but still should be able to be isolated.
Here’s my info. My entire library is MP3 and breaks down as follows. Note I have NOTHING with any DRM.
60% - CDs ripped to FLAC, converted to vbr MP3 via Lame
35% - MP3 files downloaded from emusic.com
5% - random collection of other MP3 files from unknown sources
My suspicion is that that tracks that are crashing are among my 5% “unknown origin” category.