C++ Nvidia Cg question

Answer 1

Set Debug DirectX version in the DirectX control panel and see trace output to get the reason of this failure.

BTW, I had the same situation with my pixel shader and got help in GameDev.net DirectX forum. I remember that finally I converted the shader to lowest version using SDK conversion tool, and it worked without pixel shader. According to GPU provider, this behavior is according to DirectX specification.