I had this problem a few nights ago while I was testing my new system. I was using the Rage3D tweaker, but no O/C. The next thing I did was change my aperture size from 64 to 128 and I got rid of Rade 3d tweaker and used Raid On tweaker, and I have been able to run through the test several times without problem. I am not sure what change fixed the problem, but hopefully this helps.