hi, i was using my macbook pro for more than a year now with no huge problem, but when i was going on the web yesterday, just the usual site that i go everyday, the whole screen just went blank for some reason. it wont responds to any keyboard command, it won't sleep even when the screen is closed, it seems like the whole come computer just froze.... never had that happened before and end up have to force shutdown the computer. the force shutdown has now made my start up extremely slow... and the blank screen just occur again this morning.... i have no idea what caused the blank screen to happened. both times i was just regularly surfing on websites using safari, and while is loading the webpage, the screens goes blank. has anyone else experience this???