If you were having a heat problem that would show up right away. I would start with the memory first. Try one stick and than try the other stick.
Or you could run memtest on the memory. If the memory is OK. I would start looking at the video card. Plus all your parts are Compatible with ea other.
GIGABYTE-GA-GA-X79-UP4 i7-3930K 3.20GHz, G.Skill 32gb DDR3 2133 Quad, His HD 7850 4GB, In Win Glacier 900W, COOLER MASTER HAF 932 , 256gb SSD, Win7 Ult-64bit, 32" LED TV
GIGABYTE-GA-990FXA-UD5R, FX-8150 3.60GHz AM3+ 8-CORE, Mushkin 8gb DDR3 1600, EVGA GTX 480-OC 1.5GB, Ultra 750W PSU, IN WIN BUC 101 Mid Tower, Win 7 Pro 64bit - Play around with computer