Well that was weird.
Apologies for the extreme delay in fixing the problems here; I didn’t see the e-mail about the problem until 5:00 pm Central, and wasn’t home to fix it until 9:30 pm Central.
In its template preferences, ExpressionEngine lets you save its templates as text files on your server if you desire. Back when I was building blognomic.com I certainly did desire, so most of them were set to save as files. But all templates, including ones saved as files, are stored in the database as well.
Apparently the Index file somehow got out of sync with the database; the file was empty, even though the Templates tab in the admin showed perfectly good content. I pasted the database’s template into the file, and it worked.
I’ve disabled the sync-to-file option on all templates, so I hope this problem doesn’t rear its head anymore. I’m very sorry for the extended outage.