I have a big problem.
Up to recently, there were some components that wouldn't successfully complete when system would attempt to update. Somebody told me that those NVIDIA components were no longer available from the server.

Yesterday, I unchecked those two and the Ubuntu update successfully completed.

After this, I found out that nautilus was no longer working. So I checked on a board and attempted to remove all the drivers related to NVIDIA by dpkg -l NVIDIA* & dpkg -P ...

However, with my typical luck, after I rebooted, I received the following message after trying to log on to X:

XBMC needs hardware accelerated OpenGL rendering.
Install an appropriate graphics driver.

Please consult XBMC Wiki for supported hardware

What I tried:
1- sudo apt-get update (successfully completed)
2- sudo apt-get upgrade
Reading state information... Done
0 upgraded, 0 newly installed, 0 to reove and 0 not upgraded
1 not fully installed or removed.
After this operation, 0B of additional disk space will be used.
do you want to continue Y or N
Setting up nvidia-current (304.51-0ubuntu1~natty~xup1) ...
dpkg: error processing nvidia-current (--configure):
subprocess installed post-installation script returned error exit status 2
E: Sub-process /usr/bin/dpkg returned an error code (1)

3- ..:/home$ sudo apt-get distro-upgrade (error)
E: Invalid operation distro-upgrade

I have no problem returning back to an ATI card if it would be easier but I have no idea how to install the ATI drivers and ensure that whatever is left of my NVIDIA drivers will not be in conflict.

If one of you could help me with this, I would appreciate a lot!!!

Thanks for all your help in advance.