So, I installed Windows 7 RC to my iMac yesterday. I installed all updates and rebooted it and it was fine no problems at all. Then I installed anti-virus program called F-Secure (it's a good finnish program, been running it on 4 other computers) and I rebooted again. Now it doesn't shut down. It just stays on "Shutting down" text and the circle is running. I had this same problem on my PC laptop. This isn't a big issue but I'm afraid to hold down the power button to shut down my Mac every time I use Windows. If anyone else is having this problem, all help is appreciated.