Comment 104 for bug 1069199

@Zisu: here is what I did to make it working again

sudo apt-get remove --purge fglrx fglrx_* fglrx-amdcccle* fglrx-dev*
sudo apt-get remove --purge xserver-xorg-video-ati xserver-xorg-video-radeon
sudo apt-get install xserver-xorg-video-ati
sudo apt-get install --reinstall libgl1-mesa-glx libgl1-mesa-dri xserver-xorg-core
sudo rm /etc/X11/xorg.conf
sudo apt-get remove --purge xserver-xorg-video-intel
sudo apt-get clean
sudo apt-get update && sudo apt-get upgrade
sudo apt-get install xserver-xorg-video-intel

If unity does not start check if the unity plugin is active in compiz:
run ccsm in the terminal, activate unity and solve all the conflits.