OT: Macvidcards GTX 480 problem

I'm posting here because users on this forum have experience with Macvidcards' Nvidia cards. I could really use some help.

I bought and installed a GTX 480 from Macvidcards for use with Adobe CS6 PP. When I try to enable the GPU hardware support in Premiere "Project Settings" I can not select "Mercury Playback Engine GPU Acceleration (Open CL)" for "Video Rendering and Playback" because it is grayed out and not available. I downloaded and installed the CUDA driver from Nvidia. Nvidia system settings report drivers as CUDA driver: 4.2.10 and GPU driver as 7.18.18 270.05.25f01.

My system: MacPro 3.1, OS 10.7.4, Premiere CS 6.0.1, 16gb ram, Macvidcards' flashed/modified Nvidia GTX 480.

Help with this is very much appreciated.