If you look really carefully can you still see a logo or startup page on the screen? sometimes using a torch can help, if so it is probably something to do with the back light, the most common fault is the small circuit board behind the facia panel under the screen. I would also check and make sure the wiring is OK, when it happened to my laptop it was a bad connection under the keyboard, opening and closing the lid can sometimes pulls the connections apart.
fixitmesen, March 2010
