The site was starting to throw some errors because we were still on Drupal 5.18. Finished the upgrade to 5.23 (the last 5.x release) and then on to 6.22 (the current 6.x release).
As usual, following an upgrade, some things might be weird. if so, let me know by posting a comment to this post (or start your own thread) and I'll address when I can. Some of the contributed modules (including Audio, which we used for several things) aren't being maintained anymore, so I had to disable them. But I've got User Points and Shoutbox running, as those are crucial.