My iMac is refusing to shut down, restart or launch front row and various other things! I tell it to shut down from the Apple Menu, nothing happens, I tell it to restart from the Apple Menu. I tell it launch front row by pressing menu on the Apple Remote, I get nothing by the remote and apple + esc. The volume, mute, and eject keys on the keyboard don't do anything, they won't even show they symbols on the screen! Please help, i'm starting to get worried.