Video Drivers were my problem.
At the time, the latest drivers did not fix it so I had to roll back a couple of versions.
Now it seems that the latest nVidia drivers are working fine for me.
I feel your pain.
Glad that you got a handle on it. Often, updating the drivers is the cure, but in some cases, like yours, the newer drivers ARE the problem.
There have been several nVidia and ATI/AMD drivers that had issues with the latest versions. I am mostly nVidia, and keep all older drivers on file, just in case. As programs, like PrPro, work so very closely with the video drivers, they will often point up issues, that other programs never will. Also, it seems that video card companies are really working hard to get more use out of the GPU, and that goal might be causing some issues with the newer drivers?