My itunes library went nuts. please help

I noticed today, that some of my compilations started showing up in the wrong parts of my cover flow. Before they would all sit nicely towards the end, then I saw that two of them where now mixed in with the V's, listed under various artist. Weird. I manually fix those two artist, and they seemed to go back to where they belonged, by editing the ID3 tags myself, even though those albums I purchased on itunes.

Then I noticed another soundtrack (compilation) was listed in another part of the coverflow, this time in the O's, and now I'm thinking my library somehow got messed up.

I rebooted a couple of times, and now when I view my itunes library, it list the artist as if Group by Compilations isn't checked. So now my soundtracks show up several times, mixed in with regular artist. I keep checking, and unchecking, and rechecking group compilations in the preferences, but it just doesn't work. The songs are still marked as part of a compilation.

This is really irritating me! Anyone have any ideas?