Oh. My. God.
I have nearly 10,000 songs in my iTunes Library. Today, that file got corrupted. All my playlists, gone. All my ratings (over 3000), gone. All my play counts, gone. I still have the original 13mb iTunes Library file that is now considered corrupted (but not the XML file... that was seemingly rebuilt the first time the error message was received). If you have any idea how to repair it, don't hesitate to let me know. I'm slowly rebuilding, but two years of meta-data has just disappeared. This fucking sucks.