I have been struggling with this problem a long time and finally found a solution. Everything worked great under Ubuntu 8.04 but for some reason with the release of intrepid, this part stopped working. The answer was to use Envy to first remove every installed driver and then install the 1.73 drivers. Since I updated to Intrepid I haven’t been able to do this but for some reason now I can. I think the answer lies in new Linux kernel/headers update that got released recently. Now I can safely reboot my computer without having xorg crashing and glxgears and Compiz works like a dream.