can't quit X-Server

[PuckPoltergeist]

After starting the X-Server (via kdm), I'm unable to quit it, e.g. for changing the config. The only signal X is responsive to is SIGKILL. But even then I have to reboot the system, cause restarting X leads reliable to a complete system hang. Only hard reset helps then.
This behavior is reproducable with xorg-server-1.5.1 to 1.5.3 and fglrx-8.11, 8,12, 9.2-beta1 and beta2.

The system is a x86_64 (AMD Opteron) with 1.5GB RAM and HD3650 Radeon (AGP).

Any hint, how I can solve this?

[RealNC]

Would like to know too, but I suspect it can't be fixed. fglrx has been behaving like that for me too. For a long time now.

[PuckPoltergeist]

Ok, it seems it work out of X. If I choose "console login" in kdm, X is properly shut down and I also can quit kdm and restart. Only trying to stop X from console ('/etc/init.d/xdm stop' for gentoo) will hang the system. X doesn't react on it and changing back to VT7 will hang the system. So quitting out of X at least seems to be a workaround.

EDIT: Another point: Never, never never kill the X-Server with Ctrl-Alt-Backspace. This will also lead to a crash later on.