Tony asked "Does anyone else know about a mass-V2-tag-clearing program?"

Yep - the pro version of mp3trim (mp3trim pro) does this via drag-n-drop. However, though it processes subdirectories, it only goes one level down, so you need to spend time dragging each set of album directories for each artist you have :-( However, doing 10-40 files at once is better than doing 1 file at a time :-)

This is what I use to clean out v2 tags after ripping with easy-cdda-extractor and editing with mp3-tag-studio-2... I got bit with this one too.