Problem solved. I just downloaded over a hundred Microsoft updates that I've neglected to install. Although I do still sometimes have to refresh maryrenaultfics once or twice to get the posts to appear, they do eventually; and every other problem seems miraculously to have disappeared.

There's a moral in there somewhere, I suppose.

One thing's for sure, though: no credit accrues to LiveJournal Support, who basically just left me dangling. Let us instead thank ESET: when I was about to do a virus check, it decided as a preliminary to tell me that my operating system was not up to date, and suggested I click for updates.

Light dawned....

Ah, the sun is out (though it's actually nearly nine p.m.); birds are singing; and I see little apples on the tree. They will be picked in the near future, I promise.