On a hunch, I rebuilt xorg-server and xserver-xorg-video-ati with -fno-stack-protector, and I am completely unable to reproduce the problem with those binaries. I restarted gdm 5 times from single-user mode and also rebooted the system 5 times. Given that the problem was extremely repeatable before, this is fairly compelling.
It's possible that this could explain my mysterious bug #54726 as well (different machine), though that one is not repeatable so it's difficult to tell.
On a hunch, I rebuilt xorg-server and xserver- xorg-video- ati with -fno-stack- protector, and I am completely unable to reproduce the problem with those binaries. I restarted gdm 5 times from single-user mode and also rebooted the system 5 times. Given that the problem was extremely repeatable before, this is fairly compelling.
It's possible that this could explain my mysterious bug #54726 as well (different machine), though that one is not repeatable so it's difficult to tell.