X fail: "Screen(s) found, but none have a usable configuration"

I've been running 12.04 (64-bit) for quiet a while now without any major problems. But when trying to login in today, the GUI failed to come on and was stuck at a flashing cursor. I switched to a console (CTRL-ALT-F1) to see what the problem is. Looking in /var/log/Xorg.0.log I get the following failure line: (EE) Screen(s) found, but none have a usable configuration

I thought it might be something to do with Nvidia drivers so I did a purge of the nvidia stuff (sudo apt-get purge nvidia*) and reverted the xorg.conf file to the little failsafe one that uses vesa. But this still comes up with the same error, so I doesn't look like it's the nvidia stuff that's causing the problem.

I'm really stumped now, any ideas? I assume the last update has changed something, but I'm not sure what was updated that could have caused this.

I could solve it reconfiguring the GUI by executing:

Xorg -configure
dpkg --configure -a

and restarting. In my case it recovered the previous (correct configuration).