[vtkusers] Xlib: extension "GLX" missing

[BERK GEVECI]

First thing you need to do is to find out which version of
XFree you are using. You can do that with
xdpyinfo  | head

Then, since the problem is certainly with the installation
of the nVidia drivers, I think it is easiest to re-install
them. Download the appropriate drivers from www.nvidia.com
The links I mentioned before explain how install them.
I don't know what your distribution is but, if rpm packages
are supported, that is the first thing I would try. If
that doesn't work, try to build the drivers from the tar
files. Don't forget to specify the right driver in the
XF86Config. 

Unfortunately, you might end up with multiple versions
of the OpenGL libraries (libGL.so etc) and you need to find
the right ones to use. The locations change from distribution
to distribution. I think it is common to have hardware accelerated
OpenGL, software based OpenGL and nVidia's OpenGL on the same
machine. You have to make sure that you link properly and
that the dynamic linker finds the right libraries at run time.

I hope this helps.
Berk