9800 GT video problem.?

Hey, guys. I just bought a Gateway FX 4710-UB003A, and I wasn't having any problems with it until recently, when playing F.E.A.R., Test Drive Unlimited, or GRID, the video will get these weird blue or red dots and lines in the picture, and two seconds later the computer freezes, and a blue screen comes up and it gives an error and it dumps the physical memory and restarts. What is the problem? The 9800 GT is factory overclocked. It gets hot, so i turn the fan up to anywhere from 70% RPM to 100% RPM with NVIDIA forceware. I was going to get a fan for just the video card to blow directly on it. I just bought this computer four weeks ago at Best Buy. I really don't want to get another computer, I want to fix the problem. only if its absolutely necessary would i get a new computer. The weird thing is, is that it doesn't have this problem while playing HL2 EP2, CS:S or TF2, just the three mentioned above. Can anyone help me?