I have had this problem as well. With my older rig, when I had my 965BE paired with my current Radeon 6950, I tried everything to get it to work short of installing Windows over again. Then, I looked, and at the time, I had 8GB of RAM, and I figured why not, its the last thing I have to try, and I took out 2 sticks of RAM, and that solved my problem. Not saying it will solve yours, since I have heard many issues with it, so it could be some other issue.
Best of luck to you sir.