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.