OS = Ubuntu 10.04 64 bit
Video card = N450GTS Cycllone 1GD5 with Geforce GTS 450

When I first installed Ubuntu (several years ago), OpenGL rendering worked fine. My GLMatrix screensaver rendered well.
Recently, while attempting to install other software for robotics simulation, /usr/lib/libgl.so was showing as red. GLMatrix screensaver stopped working.

I did: sudo apt-get install --reinstall freeglut3-dev build-essential libx11-dev libxmu-dev libxi-dev libgl1-mesa-glx libglu1-mesa libglu1-mesa-dev and it did not help.

The following commands give these results:

sam@Mecha:~$ glxgears
Error: couldn't get an RGB, Double-buffered visual

sam@Mecha:~$ glxinfo | grep '^direct rendering:'
Error: couldn't find RGB GLX visual or fbconfig

Please help me solve this problem.
(unfortunately, I did not make an image backup of Ubuntu....mainly because I don't know how to do that under Linux....it would have been nice to just reinstall a working image)
Thanks.