My G4 Powerbook (15-inch, 1.5 ghz) is now practically unusable after only 2 years. It will go to sleep randomly when I am in the middle of doing something and will go back to sleep almost immediately after I wake it up again. It will only stay on for about 5 seconds at a time before falling asleep again. The laptop itself feels cool so I dont think it is overheating. Nothing seems to help it although occasionally it will stay on for a few of minutes after leaving it alone for a couple of hours. I think this problem has to do with the heat sensor on the logic board. It seems like the sensor is bad and will tell the machine to go to sleep to prevent it from overheating even if it isn't. Does anyone else have this issue? It will now be very hard to diagnose because the laptop does not stay on for more than a few seconds at a time, so it is practically dead. Yes I should have bought apple care, but I really didn't expect an issue as serious as this to happen so fast. I am pretty disappointed because I am now in a tough situation with classes about to start and no Apple store near by. With all of the expenses and responsibilities I have right now at school, this is really the last thing I need. Is there anyone who could offer any advice besides just biting the bullet and sending it in for repair?