My copy of iTunes is rorted today too.
None of my music appears in the library though it's all there (when I press play it plays) and when I switch to the music store, when I switch back to looking at the library the store interface is still there. It's like back in Windows land when bits of the front window would appear in the window behind for a while. Except this seems to be permanent.
Any ideas how to fix? So far the problem is replicated in a new account, I've deleted plist files, tried to reinstall iTunes from the package (Cannot install iTunes on this volume is the error I get), repaired permissions and even tried to reinstall the combo update to 10.4.9.
My HDD seems fine, no slowdowns or noises, it passed verification.
The spotlight-like search area is greyed out when my music library is selected.
Anyone else having similar problems?