I have an ATI Radeon 9000 Pro (RV 250) which had the same symptoms - 3D applications would hard freeze. I can still ssh into the box from another machine, but killing X did nothing, so I think the freeze is actually the video card.
The suggestion above to add Option "AGPMode" "4" to the device section of xorg.conf fixed the problem. -- Screensaver freezes on Dapper (ATI Radeon 8500 LE) https://launchpad.net/bugs/38181 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
