Black screen on a Samsung R505

I have a Samsung R505 and the problem that I have is that the laptop loads correctly but only the bottom half of the screen goes black.

I can see the desktop at the top half of the screen and when I double click the top icons I can see the programs working but the bottom half of the screen is black.

When it first started to happen if I held the left edgeing of the screen it cleared it but now that doesn't work.

Any ideas would be much appreciated?