It could be the screen itself or a bad inverter. I don't suspect it is the inverter though, seeing that you can see text on the screen with a flashlight. How old is the machine? Your best bet to figure out the problem would be to contact Asus support, maybe they can narrow it down. If it is still under warranty, send it in. If not, take a look around for a new screen, as you could probably find one for fairly cheap.