system freeze with ati driver

[Miki]

Hi,

When trying to restart X my system totally freeze.
I'm running current amd64 with the following patch : drm-radeon-test.patch
(the freeze occurs also without this patch)
I'm using ati 6.12.4 drivers with xorg 7.5 (IIRC I was having the
problem with xorg 7.4 too).

I'm unable to get a kernel core dump, the box locks up completely, no reboot,
no panic, no ctrl-alt-esc, no remote debugging possible...

I have no problems with radeonhd driver, I can restart X multiple times.
The same hdd and the same graphic card on an other computer works fine.
I have the latest bios available for the problematic computer.

Xorg.0.log : http://pastebin.org/124852
verbose dmesg : http://pastebin.org/124856
memcontrol list : http://pastebin.org/124857

Any helps appreciated

Thanks in advance,
Miki

sorry for my bad english