Reset Compiz in Ubuntu 11.04

If your window title bar is gone. or you have messed the compiz in any other way in Ubuntu. Just open up a terminal and enter the following command:

gconftool-2 --recursive-unset /apps/compiz-1

Then Logout and Login back.

Edit:
As commented by zwergnase, the above command should also be followed by:

gconftool-2 --recursive-unset /apps/compizconfig-1

Solve -- Xlib: extension GLX missing on display

Recently I was playing with OpenCL in my system. Due to its dependency, I had to mess up with different packages. I even installed Intel® OpenCL™. And suddenly on next boot Something went wrong.
And this is what I did to revert back:

sudo apt-get purge nvidia*
sudo apt-get install --reinstall xserver-xorg-video-intel  libgl1-mesa-glx libgl1-mesa-dri xserver-xorg-core
sudo dpkg-reconfigure xserver-xorg
sudo update-alternatives --remove gl_conf /usr/lib/nvidia-current/ld.so.conf

Hope it helps you too.

Reference:
https://theiszm.wordpress.com/2010/06/27/glx-missing-on-display/