Comment 3 for bug 152050

The next step debugging (unless someone can spot this as a known bug) is to get a gdb backtrace from the X server.

(Assuming you want to continue debugging, and have the time to try this).

You'll need to install the debug symbols for it, which you can get via apt-get if you add the following line in /etc/apt/sources.list:
deb http://people.ubuntu.com/~ubuntu-archive/ddebs gutsy main universe

You'll then be able to install some debug packages for the X server:
apt-get install xserver-xorg-core-dbgsym xserver-xorg-video-intel-dbgsym

This will allow us to see what function names are being executed from inside the debugger.

Whilst it is working, ssh in from another machine, then run find the process number of X with:
echo `pidof X`
or just look with ps -axf

run gdb (as root, or via sudo):
sudo gdb

when that loads, type:
attach PID_NUMBER
(replacing PID_NUMBER with the process number we found for X above.)

type "cont"
(enter)

and the X server will resume. Leave it, and let it crash / hang... then (assuming it didn't stop, or abort already), press Ctrl-C on the gdb debugger, and you should get a prompt.

Type "bt"
(enter)

and this should show a function call trace of what the X server is doing.
Please post that here.

NB: any console switches, say back to VT1 etc... will drop you into the gdb console. Typing "cont" (enter) should get you resumed again.