Ok I've done some digging and it looks as so for some reason the graphics driver is disabling CUDA support (and OpenCL support as well) hence why applications (including cudaminer and cgminer) can't see or use CUDA/OpenCL.

I am unsure why this is happening ..... I think it could have something to do with my motherboard (Asus P8Z77-V) and the integrated graphics card - although it is disabled the Nvidia driver may be detecting it and disabling CUDA support.

Has anyone seen this before?