After bios update and new grahiccard the computer freezes

Im having constant problems with computer freezes every time i play a game for about 30 min. The screen either turns black, or some weird greenish color with stripes, and then i have to manually restart the computer with the restart button. The thing is that i didnt have slightest problem before installing my new graphicscard, HD 7970 ghz edition. Previously, i had two HD 5870, crossfire, and could play for hours or use graphics heavy programs for hours without any crash or freeze. I then decided to buy one hd 7970, and in the beginning, the games just crashed to desktop and i got a message that the game stopped working. I decided to update to latest bios version and the problem became worse, and the computer started to freeze instead and screen turned into different colors.

I had a similar problem about one year ago when i added 4 gb o ram, so i had a total of 8 gb of Corsair XMS3 DDR3 1600MHz CL9. I solved the problem by lowering the DRAM frequency to 1333 and made some other changes that some dude helped me with. Now, after the bios-update, all the previos changes i've done a year ago was gone. I have now tried to follow same advice but without any luck. I have reduced the memory clock to DDR3-1333, reduced QPI, but still getting freezes. I have run memtest for several hours, benchmarked with furmark, Unigine Heaven, and get no freezes at all. It only occurs when i play demanding games such as Far Cry 3 and BF3. Any advice on what to do?

I have a P55 GD-65 motherboard, i7-860 cpu, windows 8 64-bit.

Here are some pic of bios -
http://i47.tinypic.com/5drs7t.jpg
http://i45.tinypic.com/34zztis.jpg
http://i45.tinypic.com/j9xyr9.jpg