Comment 2 for bug 96819

Ah, I see the problems here. For Lucas it's probably the recent update of the nvidia driver, now he needs to install nvidia-glx-legacy. For Trouilliez it is because nvidia-glx is not installed and thus it is considered 'active', but not 'enabled'.

BTW, 'sudo dpkg-reconfigure xserver-xorg' is the way to change xorg.conf that keeps the system consistent with the debconf database (and thus keeps r-m working with it).