when i turn on my powerbook the brightness is as bright as it is when you turn the brightness all the way down to the last notch (barely visible, only if theres total darkness and you tilt it right, can you make out whats on the screen). When i push the brightness buttons they go up and down but it doesnt do anything to the actual brightness! What happened? what do I do? (i know i can use an external screen for now...) I tried restarting, etc etc etc. what else can i try?