Comment 12 for bug 466539

I think I've tracked it down a little further.

It seems that only X freezes not the system as a whole. I was able to trigger this bug from a remote computer via ssh and gather the logs afterwards. Here's what I did:

$ ssh <email address hidden>
$ export DISPLAY=:0.0
$ export XAUTHORITY=/var/run/gdm/auth-for-login-*/database
$ xrandr -q
Screen 0: minimum 320 x 200, current 1366 x 768, maximum 4096 x 4096
VGA1 disconnected (normal left inverted right x axis y axis)
LVDS1 connected 1366x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1366x768 59.9*+
   1360x768 59.8
   1024x768 85.0 75.0 70.1 60.0
   832x624 74.6
   800x600 85.1 72.2 75.0 60.3 56.2
   640x480 85.0 72.8 75.0 59.9
   720x400 85.0
   640x400 85.1
   640x350 85.1

now I plugged in the other display

$ xrandr -q
Screen 0: minimum 320 x 200, current 1366 x 768, maximum 4096 x 4096
VGA1 connected 1280x1024+1366+0 (normal left inverted right x axis y axis) 338mm x 270mm
   1280x1024 60.0*+ 75.0
   1152x864 75.0
   1024x768 75.1 70.1 60.0
   832x624 74.6
   800x600 72.2 75.0 60.3 56.2
   640x480 72.8 75.0 60.0
   720x400 70.1
LVDS1 connected 1366x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1366x768 59.9*+
   1360x768 59.8
   1024x768 85.0 75.0 70.1 60.0
   832x624 74.6
   800x600 85.1 72.2 75.0 60.3 56.2
   640x480 85.0 72.8 75.0 59.9
   720x400 85.0
   640x400 85.1
   640x350 85.1

At the moment I issued this command the screens went blank (except the pointer) as before with gnome-display-settings.
Successive calls to xrandr -q simply block until I hit ctrl+c.

I attached the output of dmesg and Xorg.0.log.
In dmesg 2495 is the time of the first "xrandr -q" 3974 the second one.

I hope this get's us a bit