Just an update on my efforts:
Some of you may have noticed that the forum has been down for the last 2 hours. I was trying to install a new version (3.0.6 as opposed to the current 2.0.2) because the new version allows much better anti-spam measures (and has many other advantages as well).
Unfortunately the new installation failed on the step that imports the old forum into the new version. Obviously the new version is no fun if we lose all our existing content, so for now I've just restored the familiar old version. (Aren't you glad that I made a backup?)
For lack of time, I am going to leave the old version running again. I hope to find a few hours some other day where I can dig into the question of why the import failed. That needs to be addressed before we can move on.