wormwood@wormwood-K42Jc:~$ sudo lshw -C video
[sudo] password for wormwood:
*-display
description: VGA compatible controller
product: Core Processor Integrated Graphics Controller
vendor: Intel Corporation
physical id: 2
bus info: pci@0000:00:02.0
version: 18
width: 64 bits
clock: 33MHz
capabilities: msi pm vga_controller bus_master cap_list rom
configuration: driver=i915 latency=0
resources: irq:46 memory:d3400000-d37fffff memory:b0000000-bfffffff ioport:e0e0(size=8)

wormwood@wormwood-K42Jc:~$ dpkg -l | grep nvidia
rc bumblebee-nvidia 3.0-2~preciseppa1 nVidia Optimus support using the proprietary NVIDIA driver
ii nvidia-current 295.59-0ubuntu1~precise~xup1 NVIDIA binary Xorg driver, kernel module and VDPAU library
ii nvidia-settings 295.53-0ubuntu1~precise~xup1 Tool of configuring the NVIDIA graphics driver

optirun glxgears

work good ....

but

glxgears

doesn't work

wormwood@wormwood-K42Jc:~$ glxgears
Xlib: extension "GLX" missing on display ":0".
Error: couldn't get an RGB, Double-buffered visual

Ubuntu 12.04

Any Help ? Thanks....

It _may_ not be a problem if the graphics work.

Proprietary drivers write their own files in place of Mesa libs. Check the o/p of

ls -l /usr/lib(64)/libGL*

in particular, where the symlinks point to.

wormwood@wormwood-K42Jc:~$ ls -l /usr/lib/libGL*
lrwxrwxrwx 1 root root 18 10月 22 2011 /usr/lib/libGLEWmx.so.1.5 -> libGLEWmx.so.1.5.2
-rw-r--r-- 1 root root 251144 8月 5 2011 /usr/lib/libGLEWmx.so.1.5.2
lrwxrwxrwx 1 root root 16 10月 22 2011 /usr/lib/libGLEW.so.1.5 -> libGLEW.so.1.5.2
-rw-r--r-- 1 root root 283912 8月 5 2011 /usr/lib/libGLEW.so.1.5.2
-rw-r--r-- 1 root root 654 6月 8 10:58 /usr/lib/libGL.la
lrwxrwxrwx 1 root root 10 6月 8 10:58 /usr/lib/libGL.so -> libGL.so.1
lrwxrwxrwx 1 root root 15 6月 8 10:58 /usr/lib/libGL.so.1 -> libGL.so.295.53
-rwxr-xr-x 1 root root 822468 6月 8 10:58 /usr/lib/libGL.so.295.53

Any Help? Please...
Thank you...

Sorry. My wife is seriously ill, and at home.
Your LibGL stuff appears to be in a mess. This one
is definitely from a proprietary driver, and the others all appear to be from Mesa and the two don't mix.

suggest remove proprietary drivers (they take an --uninstall or something) reinstall mesa, (install over) and then reinstall proprietary drivers if you want that.