Ubuntu - NVidia - OpenGl - Unity - Compiz disappear

You may find multiple topics on various internet forums describing the very same symptom:

On Ubuntu with old Nvidia cards, at some point, generally after an apt-get update or new video driver installation : compiz disappear.

There are a lot of "fixes" answered on those forums. None of them concerns the case I encountered multiple times on my laptop.

I put the description of my problem here. Hope it will be useful. At least it will be a reminder for myself :

Here is the log describing the error :
> sudo grep "(EE)" /var/log/Xorg.0.log
[ 693.341] (EE) Failed to load /usr/lib/x86_64-linux-gnu/xorg/extra-modules/x86_64-linux-gnu_xorg_extra_modules/x86_64-linux-gnu_xorg_extra_modules/...
[ 693.341] (EE) Failed to load module "glx" (loader failed, 7)

Here are some strange resulted commands :
> ls -l /etc/alternatives/x86_64-linux-gnu_xorg_extra_modules
/etc/alternatives/x86_64-linux-gnu_xorg_extra_modules -> /usr/lib/x86_64-linux-gnu/xorg/extra-modules
> ls -l /usr/lib/x86_64-linux-gnu/xorg/extra-modules
/usr/lib/x86_64-linux-gnu/xorg/extra-modules -> /etc/alternatives/x86_64-linux-gnu_xorg_extra_modules

Here is how I "solved" it :
> sudo rm /usr/lib/x86_64-linux-gnu/xorg/extra-modules