Ok I've got a problem as well. I didn't read the information about the problems with upgrading to Jaunty and using an unsupported video card - I have an ATI x850, as noted in my signature, and I foolishly upgraded to Jaunty, had no video problems except the screen blinked once in a while. I figured a re-install of the ATI driver would surely fix the problem (sorry - newb moment)
I keep copies of the ATI drivers in my /root directory so I used the uninstall script to remove the ATI driver and I rebooted. I got the low-graphics screen of death which would result in a loss of signal to my monitor for each option that I selected. I can't re-install the 9.3 driver because it is not compatible with Jaunty. I can't install the 9.4 driver (with Jaunty support) because I have a card that is no longer supported.
So what can I do to get my machine running again other than clean install? I have my /home directory on a separate partition but I've gone like a year and a half without reinstalling and I'd like to keep the streak going. As many times as I preach to newbs to make a backup image, I don't have one - poo on me. Is there some way I can set my xorg.conf to use the x850?