1. Install Ubuntu 12.04
2. Upgrade to the LTS enablement stack
3. Purge the old config via aptitude purge ~c
This will remove the files /etc/X11/X and /etc/X11/xorg.conf (and maybe /etc/X11/default-display-manager can't remember if this was caused by something else).
To reproduce this do the following:
1. Install Ubuntu 12.04
2. Upgrade to the LTS enablement stack
3. Purge the old config via aptitude purge ~c
This will remove the files /etc/X11/X and /etc/X11/xorg.conf (and maybe /etc/X11/ default- display- manager can't remember if this was caused by something else).
To fix this run (thanks to http:// askubuntu. com/questions/ 232926/ etc-x11- x-not-executabl e-error- when-startx)
sudo dpkg-reconfigure -phigh xserver-xorg