Hey guys, I was playing L4D2 today and for some reason all of a sudden my screen turned grey/white and flickered like crazy. I couldn't do anything but turn off my monitor and then turn it back on. I thought maybe it was my graphics card so I tried to update it but apparently my graphics card is up to date. What should I do? I just got the computer today too. It's a dell xps 7100, 1055t processor, HD 5870 graphics card. Thanks.