You may want to run Memtest 86+ one stick at a time to check for a bad stick. I've found it pretty useless with 8gb of ram and I'm sure that 6 is no different. Memtest 3.8 is much more stressful plus you can run 8 threads of it which will really stress your ram. Sometimes that won't even fail but if your rig starts acting funny during the test you'll know that you have issues. Intel burn test might be your best bet. I would give that a shot, first. Good luck man. I was having very similar problems when I upgraded to 8gb of ram. Ran Crysis fine but was having odd freezing and the occasional hard lock when gaming. A bios update fixed my problem.