If your installed the newest Xorg 7 with Debian or possibly with any distro you will need to do a little something different when you install the Nvidia module kernel module for your vid card. The new Xorg version 7 has switched to a modular driver type with a new path. If you don't give the "--x-module-path" option to the Nvidia installer you will get this error when trying to start your new X server "(EE) Failed to load module "nvidia" (module does not exist, 0)". If you do then you have to reinstall the Nvidia module with the option below. It should fix your problem.
sh NVIDIA-Linux-x86-1.0-8762-pkg1.run --x-module-path=/usr/lib/xorg/modules