Okay, X is back up and running now, basically the way it was before. For reference and for anyone else with the same problem, this is a synopsis of the problem and solution:

Problem: When trying to get 3D acceleration working, I loaded something from the drm-trunk of xfree86; this was version 4.2.99.2, so everything depending on it being 4.3.0 freaked out. In retrospect, that was a bad idea.

Although I did a few things, I _think_ the following steps fixed it:

COLUMNS=150 dpkg -l | grep xfree86
Find the name of the drm-trunk version.
apt-get remove what_ever_the_name_was

The part that stumped me for the better part of a day was that drm-trunk did not have a version number, but a date attached. Therefore, neither
COLUMNS=150 dpkg -l | grep 4.3.0 or
COLUMNS=150 dpkg -l | grep 4.2.99
would show this package.


Anyway, is there an easy way to get an ATI Radeon card working under Knoppix hdd-install? It was working (and still is) on the CD.