I upgraded my Ubuntu machine tonight from 10.04 LTS to 10.10. When the machine came back up the video was totally messed up and I couldn’t see the login screen. Apparently CTRL-ALT-BACKSPACE was disabled at some point to kill the X server and boot you back to a command prompt. Googling around I found the answer: Alt-PrintScreen R E I S U B. As in hold down Alt-PrintScreen and while doing so type in each of the letters. This will essentially force a reboot.
I then booted into recovery mode from the options given by the GRUB boot loader. When given the choice I chose the failsafe video mode which apparently is supposed to boot into a low res screen but in my case actually booted me into full resolution. I then chose System->Administration->Additional Drivers and it found a new version of the NVIDIA accelerated device driver. I had it download and activate that and after a reboot I was back in business.
While searching around I found many people who said never to do an update of Ubuntu, only fresh installs. I found that kind of odd because this is the first time I’ve ever had an issue with the updates. Right now I’m in the process of upgrading to 11.04 so we’ll see how that works out 🙂