I was manually updating to new files from the CVS, and seem to have royally screwed something up. I've done such updates dozens of times in the past and never had a problem, so I'm definitely not a newbie when it comes to that.
I went through and updated the MySQL database according to the updated schema, and then uploaded the new files from CVS. The first problem was that my subSilver font size was immediately shrunk to 0 pixels, so I had to go edit the database to fix that.
Then, once I could see what I was doing, I realized that while all the posts are still in the database, and the correct post counts for each forum appears on the index page, when I click inside each forum, only announcements are visible! Nothing else can be seen... I tried resyncing, but to no avail.
I did a backup of the database using the admin panel, but it only contains certain parts of the database, apparently (I did not know this until it was too late) and restoring it does not help.