Don't know if this is the case in your situation, but I had a simmilar experience, before I did some housecleaning in Itunes.
For example, I noticed that I had two Huey Lewis albums show up, even though I just had one.
One was "Huey Lewis and The News"
The other was Huey Lewis And The News" (Capital A in "And") Made it show up as two different artists.
Went through and made sure that everything was spelled exactly the same on all songs/album names/etc and that fixed it.
Hope that helps some.
