NVIDIA X Server Settings error unable to use the NVIDIA X driver.

Hi there,
The NVIDIA server gives me this error in Ubuntu. I don’t know why the error says that I don’t use the NVIDIA X driver since I have the latest update of it. Is a little bit weird and can anyone help me to make the right configurations? Why I have this error, what is the main error?
Thanks!

NVIDIA X Server Settings
You do not appear to be using the NVIDIA X driver. Please edit your X configuration file (just run ‘nvidia-xconfig’ as root), and restart the X server.
OK
