Invalid File Formal - During Sync?

I'm doing a sync right now, and the player is currently rebuilding the database. The screen had gone blank, so I turned the volume knob to wake it up. The message "Invalid File Format" popped up for a few seconds, then the normal Sync display came up. Has anyone seen this?

As I typed this, the sync finished and is continueing to play the song it was before the sync.. all seems well.

2.00final w. emplode. Latest Hijack.