It's like deja vu all over again, I hope.
What happened was, as a consequence of a power failure a couple of weeks ago (or possibly my memory problems of an even earlier vintage), one of the databases that backs this weblog got corrupted. It only caused problems (or appeared to) for a small number of URIs, but still a corrupt database isn't a happy thought.
Last night, I used my backup tool to extract the URIs, patch the broken ones from my staging machine, and load them back up into a new database. (Because I'm proceeding cautiously.)
This morning, I threw a switch on the server to begin using the new database.
You aren't supposed to be able to tell. But if you see something that looks wrong, please do let me know.