Arrgh.. "Operation failure exceeded maximum retry count", and the empeg still says 'Synchronizing' on it.
..after rebooting and rebuilding the database, it said "There is no file with FID 2 on this device."

What I did:
Added four Yngwie Malmsteen albums in FLAC format to a new playlist under 'Metal'. Sorted them to taste, hit 'Set Playlist Order', and then synchronized.