Possibly something wrong with the onboard video...or a bad connection somewhere. The question is, does it boot up completely when it has no video output. It's obviously not the inverter or backlight (those would be the easy ones to fix), so the best you could do is to disassemble the laptop (checking for obvious problems while it's apart), put it back together, and see if that solves the problem. I've actually fixed stuff just by taking it apart and putting it back together. If that don't do it, probably not much else you can do besides a new system board.