Finally got CUDA working. Fast and effective.
This works for various versions of Premiere Pro. CS5-CC as far as I’m concerned.
If it’s greyed out, then run notepad as admin, open new file, open the “cuda_supported_cards” in the Adobe folder and add your graphics card. Then right click on desktop and open up the NVIDIA control panel and click on “manage 3D settings” and add the program to the list (in this case Premiere Pro CS6). Scroll down to the “Multi-display/mixed-GPU acceleration” and select: “Compatibility performance mode”, click apply. Then restart Adobe Premiere and it should be activated.
Enjoy the CUDA yumminess. ☺