As in summary, commit 5f846360c46f5a989f5d0fde6d251cdbd61d4968 causes X to lock at startup and my machine to reboot with xf86-video-ati from git. Reverting that commit fixes the problem. I can't provide information about the bug or a significant Xorg.0.log because the lock and reboot is so sudden that most of the time the Xorg.0.log file doesn't get written and whenever it exists it is empty. A "good" log is attached to this post, my xorg.conf will follow. I'm currently using a 2.6.31.2 based kernel, xserver 1.6.4 with the DGA patch, mesa from git (branch 7.6) and libdrm 2.4.14.
Created attachment 30181 [details] Xorg.0.log
Created attachment 30182 [details] xorg.conf
problematic commit was reverted: 1b25bad2d8ebe481ffb4b0fd3a85ab636bd4fec2
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