I was having this same issue on a brand new build... Quad Core i5-750 Geil DDR3 PC3-17000 4GB (2x2GB) Asus P7P55D Mobo Radeon HD 4870 After trying a multitude of things to fix it I finally solved it by manually setting my DRAM voltage to the Geil recommended 1.65v (for some reason the auto...