Unbeknownst to me, the script handling comments got turned off. While it offered a wonderful reprieve from comment spam, it also prevented legitimate comments from being posted. I have now turned the script back on, unbeknownst to my ISP system adminstrators, who I think may have turned it off the last time... (I did tell them they could turn off the trackback script, but I guess they got carried away.)
Anyway, it's back on although running slowly. If the page seems to churn without posting, don't worry. More likely than not the comment has been submitted to the database, and the next time the site rebuilds itself the comment will show up. (Try refreshing the front page and hopefully it should show up, but even if it doesn't, it's probably still in the system somewhere.)
This mess is all the comment-spammers' fault. Assholes. I know there are some serious civil liberties concerns with pressing the trespass-to-chattels doctrine to Internet traffic, but in situations like these it sort of seems like a nuanced application of it might be appropriate.