I've been having this problem since iTunes 8. I had hoped iTunes 8.1 would correct the problem but alas, I'm not that lucky. Basically, if I try to restart or shutdown the Mac, it will tell me that it can not and to close iTunes first. When I close iTunes...it immediately reopens over and over. I just have to keep telling it to close, sometimes more then 10 times, and eventually it won't reopen and I'm able to restart or shutdown the system. Am I the only one experiencing this? I haven't seen any threads on it.