Hi ChiggyChiggy,
There are several threads about the problems some users have with the Gracenote supported auto-tag feature. It works for some and doesn't for others. The fix would require a rewrite with different Gracenote provided library files (*.dll). The reported new owners of Winamp may take this on, but that remains to be seen.
I suggest you use a another free app with an auto-tag feature for tagging your music files, like Mp3Tag (link below). It supports a large variety of formats, not just mp3s.
http://www.mp3tag.de/en/