My iMac went off the grid tonight while I was watching something from my iTunes library via Apple TV. When I went upstairs to check it out, my auto-sleep 10-minute warning was popped up. When tried to dismiss it, it just popped back up, again, and again, and again. The window wouldn't go away, so I forced the computer to shut down by holding the power button until it powered off. When I turned it back on and selected my user account, it would not allow me to enter my password. I had use of the other controls on the keyboard, like volume and brightness, but none of the letter would type, and the computer just responded by giving me the error "beep". I tried logging on to the Guest account because it does not require a password, and upon successfully logging into the guest account, tried to use the keyboard within an application. Every time I hit a letter, the screen would flash as if I was taking a screen capture. When back at the login window, I would try typing my password (without any characters or dots being added to the password box) and then I would hit enter, which did nothing but put my computer to sleep. I've tried replacing the batteries, cycling the power, turning all connected devices off (Apple TV, MacBook, etc), but nothing seems to work for me. HELLLLLLLLLLP!