Blogger, you old scoundrel. We meet again.
Blogger's crack support team ascertained that it was my use of SFTP over FTP which caused the error. Nevermind that I was using FTP when this problem arose, but hey. It works now, and I can quit posting at LJ. Oh, hooray. But go check for the handful of updates there in case you missed it and you just can't get enough of me, giggle!
One annoying thing of note is that my old commenting system, implemented on my server before Blogger added built-in commenting, has vanished, and with it any comments left in the past year and a half. Grrr. Rather than set that up again, I might as well let Blogger's version take over. At least it seems to support line breaks.