Tried to wake my 24" white iMac from sleep yesterday and discovered that it was off. Pressed the button in back but no go. Unplugged and replugged, pressed the button and it fired up fine. Surfed a bit, then put it back to sleep. Came back about 3 hours later and it was off again. Unplugged and replugged, pressed the button and nothing. Tried it a couple more times just to check, and no go. Any ideas? I've had this computer for a little over two years. Bought it used and bought Applecare which expired on.... Nov. 16th. Beautiful timing or what. Thanks very much for any help on this.