I'm on Kubuntu 6.10, AMD64. I'm trying to install the driver for my graphics card (Gainward GeForce 7800GT). I downloaded the newest driver from nvidia.com. Downloaded the most recent driver (1.0-9746) and installed it.

It all seems to work fine, but when i save the configurations to xorg.conf, it can't find any screens, so i can't run x. And it says something about the nvidia kernel module has the version 1.0-7184, and the driver is 1.0-9746. So I decided to try and download the driver similar to that, x wouldn't start then either. So after installing one of them, xorg.conf won't work, so then I got to delete it, and rename the backup and go back to the beginning.

What should I do?

Try booting to runlevel 3 and run /usr/bin/nvidia-xconfig. It's the nvidia config utility that comes with the driver.

Check the logfile /var/log/Xorg.0.log; it might reveal the problem.

Further:
Have you tried following HOWTO: Install the Nvidia driver on Edgy Eft.
A similar thread worked for me for Dapper.