I have an issue with XBMC thinking that several albums are various artists albums. One of the developers from the XBMC forum has asked me to provide him the exact tag that is being used for album artist.
I’m guessing it is “ALBUM ARTIST” or ALBUMARTIST?
http://wiki.xbmc.org/index.php?title=Preparing_your_Music
Personally, I don’t like the fact that it even tries to figure this out for me but you take the good with the bad I guess.