Hi, I have two problems with my Nvidia GeForce 8400 GS, brought 2 months ago. 1: When I start the computer, it starts but I can't see anything on the screen, if I restart it, then it shows up. 2: When working, the screen goes black and then it comes back. Like, I am typing, and the screen goes black and then it comes back again. What shall I do? Quick help is appreciated. Thanks, Ratul