To keep you grphics drivers at the latest levels you should use the PPA solution

try this

0) Remove manually installed driver
sudo /etc/init.d/gdm stop
sudo /usr/bin/nvidia-uninstall

1) Add source
sudo nano /etc/apt/sources.list
deb http://ppa.launchpad.net/nvidia-vdpau/ppa/ubuntu jaunty main

3) Add key
sudo apt-key adv –recv-keys –keyserver keyserver.ubuntu.com CEC06767

4) Install
sudo apt-get update
sudo apt-get install linux-headers-generic nvidia-glx-185