Comment 44 for bug 247376

I can confirm bvidinli_ehcp's steps work. To clarify a bit -

(1) Load the recovery mode for the latest installed kernel on the GRUB boot list
(2) When the recovery menu loads, select the option "Drop to root shell" (or whatever it says to that effect)
(3) Open /etc/X11/xorg.conf in a console text editor - joe, vim, vi, whatever. I recommend Joe (you might need to sudo apt-get it) because it's easy to use
(4) Go to the "Modules" section. Either comment our or delete the line referencing "fglrx", and make an identical line, but substitute "ati" or whatever in place of "fglrx".
(5) Go to the "Device" section. You might see the line

Load "glx"

I replaced that line with -

Disable "glx"

(6) Exit Joe/Vi/Vim/Whatever. You can now try startx. If it works, you need to restart your computer to log in as a normal user (startx will load the root account)

Hope that helps.

Andrew