Comment 7 for bug 33617

Note my "Bug #39333:
Thinkpad T22 - X.org/GDM freeze GPU when docked (Flight 6 +)," which reported this on the T22.

I do notice two related issues that will (also) ruin one's experience trying to get gdm to load at boot:
-X.org socket cruft in /tmp doesn't appear to get cleaned by the boot process (possibly fixed already?), and
-When /tmp is missing, it may get recreated with the wrong permissions. (I'm pretty sure I did -not- do that manually, but, again, haven't been paying enough attention, don't have enough time to devote to the problem right now.)

After correcting those issues, I somehow managed to get X.org and gdm to come up on my last boot; for a while, it was equally toast even while undocked. I'm not sure if this has cured things or bought me a ticket in the one-time-in-four type crapshoot.

I would say that the note in the thread linked -- http://ubuntuforums.org/showpost.php?p=917923&postcount=12 -- adds fuel to the idea that this is a kernel issue, and on next boot I'll see if disabling the direct-rendering module improves anything.