You likely had a partial upgrade happen. The driver needs to be made to
work with the linux kernel so certain kernel modules are needed as well as
the driver. I would suggest that you do either of the following. You can do
an upgrade from the CLI (sudo apt-get upgrade) or you can install another
GUI and work from there. I always have a second GUI just for that reason.
(sudo apt-get install xubuntu-desktop)

If you have broken packages then try: sudo apt-get -f install

If this does not fix it then you can re-boot and use the recovery mode to
fix graphics problems. An alternative would be to try to boot an older
kernel as the driver was already working with that before things went awry.

I used the GUI drivers update app, the one that is used for non-supported
drivers. I don't know the command name. The error messages I am getting
from X say that the driver does not support the GPU. Which makes me wonder
why the install app thought I should be using it. Anyway. can I use apt-get
from the command line to uninstall the driver update?

Replying to my own email, here is how to do it from another X windows
system, assuming the two systems are connected either locally or over the
internet.

Open up a terminal window on the other Linux system.
In the terminal window start a remote shell with X enabled on the sick
system.
$ ssh -X

Then, as root, run the driver update app.
$ sudo /usr/bin/python /usr/bin/jockey-gtk

When the app opens on the other system it should come up after a brief
pause with the current non-working driver. Press Remove and wait. Then
reboot the sick system.

This will probably work for other video drivers as well. YMMV. Note that
the man page for ssh states that the -X switch opens a possible security
hole. This should only take a couple of minutes but be aware of the risk.

The only system-specific information here is the name of the app. This may
vary from release to release of Ubuntu but that is what it is for release
11.