You need to git clone the repository, go to linux-core directory, then make, and then copy/overwrite drm.ko and radeon.ko under /lib/modules. Finally, depmod -a and a reboot or gdm shutdown plus rmmod drm, rmmod radeon, modprobe radeon should get the new DRM driver into use.
The problem affected some of the Radeon 9500 - X800 cards. Including mine, though I found a workaround some time ago already even though I didn't really understand what the code is doing etc. -- nested Xgl crash, ATI r300 https://launchpad.net/bugs/39759 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
