Are you completely uninstalling the driver prior to installing the new one? Also with the new nVidia package there is an option during the install to do a "Clean Installation" have you tried that?
When you reboot after uninstalling from Safe Mode, what driver is it using when you boot up normally? Is it the Standard VGA Adapter driver? When you login after uninstalling the driver, does your computer connect to Windows Update and start downloading the driver from there?