Unable to parse X.Org version string

After this error
"unable to parse X.org version string"

...
update-alternatives --config gl_config
config gl_conf
ldconfig
nvidia-xconfig
...
Then
WARNING: Unable to parse X.Org version string
....
try before reinstall:
sudo apt-get install linux-headers-$(uname -r)
sudo apt-get install build-essential pkg-config xorg-dev

If anything goes:
sudo apt-get install - reinstall xserver-xorg
or try EnvyNG
http://albertomilone.com/nvidia_scripts1.html