It looks like the compatibility test used a texture format the 7900 GTO does not support. We have improved texture format compatibility based on the tech test results so most likely this problem has been already fixed. I'll investigate this further when I get back to office on monday.
Ok, I investigated the issue. The compatibility test does not work on NV 7900 because the test requires D3DFMT_A2R10G10B10, a texture format not supported on NV 7900. We have since then added a fallback to another texture format in case the device does not support it. So I don't see any problems running the game on NV 7900.