[Frozenn]

I just recieved my second gtx 680 today and once i installed it, the screen goes black right before it boots into windows and then restarts. ive tried both video cards by themselves and it works great. but it doesnt post once they are both installed. im not sure whatelse to do, ive checked all the settings in my BIOS and i cannot get it to post with both cards installed

850w corsairTX850
gigabyte z68x-ud3h-b3
evga gtx 680 sc+