My Dell Precision M6600 screen has recenlty started flickering when it's been plugged into the mains. It seems to be completely random. It sometimes goes for hours and starts fliskering or starts when I boot up. When I unplug the adaptor the flickering stops. I thought it was a faulty adaptor but I've just got hold of a brand new spare one and the same thing happens.

Any suggestions? Graphic card? Power socket?

Scott