A You may notice with new Ubuntu 10.04 Lucid Lynx come new version of Xorg, and with new Xorg comes new problems.
The old nVidia 185 are incompatible with the newest Xorg.
The 195 beta nVidia drivers work with newest Xorg.
*195 drivers are beta, You are installing them at Your own risk...
First, You need to add the Nvidia Vdpau Team PPA to our package sources. Open up a Terminal and type:
sudo add-apt-repository ppa:nvidia-vdpau/ppa
Next type:
sudo apt-get update
After that, You need to installt the nvidia-glx-195 and nvidia-195-modaliases packages:
sudo apt-get install nvidia-glx-195 nvidia-195-modaliases
When it's done restart computer, after that open again terminal and run:
sudo nvidia-xconfig
And You're done.
Eoin 
