They'd been working on it this afternoon, but sent me a message to tell me they couldn't find any issues. The next thing I know, the forum is back to where it should have been (save for the last 24 hrs).
I'm taking a fresh backup now, as the one that had been there disappeared at the same time as the forum came back up to date. I think the best plan of attack might be to move to a fresh server and kill this one off, but I'll keep you posted.
I have noticed recently that literally every time I visit the forum, which admittedly, isn't as often as I did 10 years ago, and despite checking the "log in automatically" box, I have to login before I can do anything.
@DaveB, if you're reading this, I think you may have sent me a PM which I never got to read and is now lost in cyberspace. Any chance you could resend?