I have a Mid-2007 Mac Mini and I've noticed every couple days, when I log out of the secondary account, it takes a relatively long time to return to the login screen. The blue screen sits there for maybe 30 - 40 seconds, but then when it returns to the main screen the whole machine freezes. The only thing I can move is the mouse, I can't click any of the buttons such as restart, sleep or get back into my account. I always have to do a hard shutdown. Has anyone else had this problem before? It's really irritating!