One of the hard drives in the server this blog resides on started malfunctioning just after midnight Saturday (UK time; about 4AM EST).
The server is running again for now, but I've put in a support request for a drive swap on Monday morning. As it's part of a mirrored drive array the server will be offline for a few minutes while my hosting provider installs the replacement, and may run slow for a few hours thereafter as the controller brings the new drive up to date.
Of course this happened just as I had a cracking idea for a substantial new blog essay, but I think it's prudent to leave posting it until after the hardware is fixed ...!