itunes song will not delete and I can't edit the info

I added some songs to itunes 9 and now i want to delete one of them. I tried using delete, right-click delete, and edit delete. The window that asks if i'm sure I want to delete the song from the library doesn't even pop up. It's like the song isn't even there. It still played when I clicked on it but I can't edit the info either. I'm unable to click on the info boxes and the tabs for lyrics and artwork are grey. Then I realized I should just delete the actual file from the folder. That deleted from the trash but now the song says it can't locate the file and I have an exclamation mark next to the song name and it still won't delete. I have over 5,000 other songs and have never encountered this problem. I've deleted other songs since using itunes 9 and it has been fine. Is there something wrong with the song file? Please help!