Try out intel driver (xserver-xorg-video-intel). I had same problem in Dapper, moved to Edgy and had to use VESA driver till I found intel driver. Now I have DRI. Unfortunately it give me only additional 100 FPS in glxgears (now up to 600), but it's better than nothing :)
Warning - I also experienced hard-lockups. Also You can not switch to console. i855GM on Dell Latitude D505 -- no direct rendering on dapper with i810 chipset (855GM) https://launchpad.net/bugs/42049 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
