Switch from source installed Nvidia driver to one provided by the package manager
Some weeks ago I switched my (now slightly used) Dell Latitude E6520 from Ubuntu 10.04 LTS Lucid to Debian Testing (Wheezy). Because at the time, the Nvidia driver available through the Debian APT repos wasn't new enough to support the bleeding edge NVS 4200M video card that came with the laptop, I installed the Nvidia driver from source. Now that the driver available through APT supports my card, I decided to switch to that. The process is quite easy and quick.
sudo /etc/init.d/gdm3 stop cd ~/Downloads sudo ./NVIDIA-Linux-x86_64-270.41.06.run --uninstall sudo aptitude install nvidia-kernel-dkms nvidia-settings
At this point, start GDM back up or just reboot and that should do it. One issue I had was that after stopping GDM, I had no network, since Network Manager seems to be a GUI only network client. A simple temporary workaround is to add "iface eth0 inet dhcp" to /etc/network/interfaces and run "ifup eth0" (don't forget to remove this line later, else Network Manager will figure you want to manage this interface manually and ignore it).
Now you'll get Nvidia driver updates as part of normal system updates thanks to the great work of Debian NVIDIA Maintainers.
For me, switching to the Debian packaged driver also solved errors like:
X Error: BadWindow (invalid Window parameter)
I got above when attempting to run AssaultCube and screensavers like glmatrix (provided by package xscreensaver-gl).
Long live Debian! I'm really loving Debian Testing on this laptop thus far.