Originally Posted by
gradinaruvasile
If you boot and get the black screen:
1. try to reach the first virtual terminal VT1 (ctrl-alt-f1), and if you can, log in then stop gdm/lightdm with "sudo service lightdm stop".
2. Then unload fglrx: "sudo rmmod fglrx"
3. See the x server error messages: "cat /var/log/Xorg.0.log", copy that file to your desktop "cp /var/log/Xorg.0.log ~/Desktop" (it will be overwritten at next x start) then attach/post it here.
If you want to start lightdm, remove the /etc/X11/xorg.conf file: "sudo rm /etc/X11/xorg.conf", then start lightdm/gdm with "sudo service lightdm start" (this is for lightdm).