Matt - I'm trying now to track down exactly what has occurred, but reviewing my backup catalogs.
One thing is for sure, ALL my music tracks have been modified (their time stamps changed), and I've not changed them. This of course caused my backups to explode (I have versioned backups), as 400G worth of FLAC files were re-backed up.
MC, starting on 3/18 at 5:54pm, starting updating my FLAC files. The time stamps on the tracks show changes occurred several per second, and not in album order. Perhaps it was either of these changes:
12.0.459 (3/18/2008)
6. Changed: Getting cover art and analyzing audio are enabled by default in auto-import options.
10. NEW: Reads and writes track replay gain and peak values to MP3 id3 tags that is compatible with several other players.
Can you confirm? I'm not sure its a good idea to have MC running in the background updating every track - this has at large external impact as can be seen.