Yup that sounds like a dying monitor to me. My initial guess/troubleshooting approach would have been similar to yours, and it sounds like your GPU and CPU and mobo/ram are good.
One other thing you could do if you want to double-check is run the GPU stress test in OCCT (google it) and make sure to click the "error checking" box. Keep an eye on your GPU temps and see if you can do something to get the green artifacts to occur. If they occur and OCCT is not reporting any errors, then that pretty much confirms that you're not having a hardware problem, you're having a monitor problem.
Hope that helps.
Thanks, I ran occt and received no errors. I'm going to pick up another monitor today, and since I still have both 6950's guess I'm also going CrossFire.