Just checking as though new here I have just recently resolved this issue.
Did you install the actual opengl nvidia driver having first closed your X session?
When restarting your X session did you see the nvidia splash screen?
My set up is simular to yours and the biggest headache I had was ensuring I got the right nvidia driver for my system. [ nvidia-installer-1.0.6.tar.gz && nvidia-settings-1.0.tar.gz ]