Comment 17 for bug 1054257

Found a fix for my problem and it now working.

Overview of my problem:
Ubuntu 12.10 + NVIDIA GeForce 9300 GS
Unity do not start Ubuntu 12.10 + Compiz (opengl) - Fatal: glXQueryExtensionsString is NULL for screen 0

What I did to solve this issue:
re-installed the nvidia drivers following this tutorial: http://www.dedoimedo.com/computers/ubuntu-quetzal-nvidia.html

   sudo apt-get install build-essential linux-source
   uname-r
   sudo apt-get install linux-headers-`uname -r`
   sudo apt-get install nvidia-current
   sudo /sbin/lsmod | grep nvidia
no nvidia found, so:
   sudo depmod -a
   sudo modprobe nvidia_current
   sudo /sbin/lsmod | grep nvidia
now it is ok, with count 0
   sudo /etc/init.d/lightdm restart

unity is restored! yay!

Hope this helps someone.

J