Take a flashlight when the computer is turned on, shine it on the screen and look very closely. If you see a a very faint image then you are in luck, it is not the LCD cable that has come loose. it is either:
- The inverter
- High voltage transformer
- The lamps in the screen
- The lamps that actually supply the light for the back-light.
There is no way to tell which one is causing the actual problem, but the easiest and least expensive is the inverter.
If the problem turns out to not be your inverter, then it is most likley your lamps.
If your screen is totally blank, then you are going to have to check your LCD cable. It can either be lose, or it needs to be replaced.