I just installed the nvidia drivers as described in the installation instructions:

cd /usr/src
tar-xjvf kernel<TAB>
install-nv<TAB>

I found I needed to hit ctrl alt F1 to get out of gdm before running this installation. Anyway, after the installation script finished, it tried to go back into gdm. When this happens, all I get is the nvidia wallpaper. I think mythtv is being stared, cause I can hear the TV sound playing, but I can't see anything but the nvidia wallpaper.

Any help greatly appreciated. BTW, I tried searching for this problem but didn't find anything.

I experienced the same Problem when I tried to install the Driver for the first time. Noting worked anymore.

I reeinstalled knoppmyth and downloaded the most actual driver Release
(NVIDIA-Linux-x86-1.0-7174-pkg1.run)
from Nvidia.
With this one everything worked flawless (even TV-Out)
You might try it without reeinstalling the complete System

I first had problems with the installation cause I didn't know how to exit X in Knoppmyth so I'll post it in the case you're also not a Linux Geek
(root@vdr:~# /etc/init.d/gdm stop)

I also had problems compiling the provided NVIDIA driver when upgrading to R5A12 from R4A5 and the NVIDIA-Linux-x86-1.0-7174-pkg1.run driver worked for me too.

FYI