GDM login corrupts X on Intel 82Q963/Q965 Integrated Graphics

Question

After updating my kernel and a few libraries last night, I restarted my computer to experience Linux 3.1. After I logged in, GNOME-Shell appeared extremely corrupted. The screen was zoomed in, and would flash wildly between different, overlayed sections of the screen, wherever I placed my mouse. I could make out a few things, but depending on my mouse's position, the screen might repeat the same segment of the desktop several times (if I have a terminal up, I can only see it at a certain position, and I see the window three times spread horizontally across the screen). If I moved my mouse all the way up or down, I saw corrupted artifacts.
Now, if I try to drop to a tty, the screen turns to a stark blue color, or grey (probably dependent on where my mouse was when I switched). I can easily switch back to the X display (Ctrl+Alt+F7), but it's still corrupted. If I do manage to pkill X using the terminal in the shattered X, the GDM login comes up again, but now with the same corruptions and distortions as in the Shell. All I can do is restart.
So, last night, I did restart after this first try with linux 3.1, to see if it wasn't just a mistake. Somehow, GNOME-Shell came up completely normal, and I thought it was merely an anomaly. Turns out, when I started my computer this morning (and restarted it fifty times since), it turns out the Shell working after the update was the anomaly. I don't know why it didn't break again that single time.
I'm currently typing from this same computer using just X (startx after logging in at the tty, no GDM). It appears normal, and playing videos and running composited applications (like Blender) works fine.
I suspected it might be an issue with the kernel, but I don't know of any package I could downgrade to to test this. Even if I could, I'd rather use the current stable kernel. Does anyone know how I could further diagnose the issue, and if this belongs in Multimedia or Kernel instead of Applications & Desktop Environments? For now I can't really tell which piece of software is the culprit, but it seems likely it could be the Shell (even though the Shell wasn't updated before or during this incident).
Last edited by ScionicSpectre (2011-11-10 02:13:21)

Answer 1

Turns out I may have found the culprit after all. After changing the gnome-control-center option under System Info to FallBack Mode, I was able to log in successfully... but only just once. Then, the same thing happened as before- every single log in resulted in a borked video output. However, when I start GNOME from .xinitrc with startx, Shell or no Shell, it consistently behaves as expected.
So, I think it's safe to say that something which happens between the login screen and the session is destroying the video output in some nefarious way. This still might be vaguely related to the kernel, but at least we know it's probably either the kernel or GDM itself (most probably GDM). So, I'm going to uninstall GDM and delete pacman's cache so I can try to install the latest version from scratch, and see if that fixes the problem. If not, I guess I'll be logging in with SLiM or something similar until this gets ironed out.
Quite annoying. Anyway, here's a short video of the breakage. Remember- once it's broken, only a restart will fix it. The glitches persist even when you head back to GDM, and ttys are always displayed as a solid, flat color, nothing more.
http://www.mediafire.com/file/ib79r6pc0 … dmbug.webm