I'm not sure if this problem is related to WINE or mp3tag, but I would really appreciate you to have a look at it.
When selecting a range of files using shift-click in WINE, the fields does not automatically change to "".
However, if you select the files using ctrl-clicks, the fields change to where it should (ie. track number, or "album" when selecting files from different albums)
This caused me to change a selection of 50 mp3's to the same values as the first mp3 (luckily the undo button worked
)
WINE was configured to use "Windows XP"