So i was using my 15" powerbook 1Ghz yesterday and all of the sudden the screen went VERY dim. I could barely see the desktop or the open windows. It was plugged in at the time and the battery is fully charged now and it's the same. I don't understand what happened. The screen was bright and normal and the next second it was almost as if it was turned off. Restarting does nothing. Adjusting the brightness does nothing. It doesn't make any darker or brighter then it is. Please help.