Comment 11 for bug 494166

To sum up once more, please note that the problem is the virtual package xserver-xorg-video-5.

Nvidia-glx 185 (in lucid repos) does provide xserver-xorg-video-5;
Xserver-xorg-core 1.7 (in lucid repos) is in conflict with the very same xserver-xorg-video-5.

The Nvidia Graphics Drivers from www.nvidia.com does not provide such a package and is not in conflict with the new xorg 1.7.
Also one can use the great PPA of sevenmachines (Nvidia PPA) and use either stable 190 or beta 195 driver.