For a while now, my MacBook Pro would occasionally refuse to shutdown. What would happen is the shutdown would go normally until it hits the blue screen. It just hangs there with a spinning wheel endlessly. I've tried everything possible (Disk permissions/verification, OnyX, ending processes from applications, AppleCare, etc.) and it is still happening. Anyone have any tips? P.S. This usually only happens after continuous use for a few hours, even if it's only light usage.