I had an unrelated problem where the wrong album art was showing up (because I had ripped the songs from a compilation CD I had created - it just seemed to pick one randomly from the songs on the disk

).
I used a free tool called
MP3DirectCut to resave the file - all I did was open, play a bit of the song, and save and it removed the album art.
I then used Mediamonkey to get the correct art, but you could obviously skip that step.