Bug#571535: Workaround

[Loren Cannon <loren.cannon@gmail.com>]

I'm far away from this computer, so

First, switch to a console (Ctrl-Alt-1)
First, slay gdm (hard when you can't see the pid using ps -A, so redirect the output to a file and use vi to fiddle with it)
Then run Xorg -configure
Edit the ~/xorg.conf.new
    Fix the HorizSync and VertRefresh under the Monitors section
    Disable Hardware Acceleration
Test the new configuration using Xorg -config ~/xorg.conf.new
Replace your real xorg.conf with ~/xorg.conf.new

You should have a nice, non crashing X Server with Gnome Desktop.