Yes, that's right, something bad happened. Not to me, to my site. It was probably a server problem.
However, I was stupid. I did not immediately back up, because the site was already not working. And I hadn't backed up at all. I thought I had.. but apparently I hadn't. There were some backups listed, but then it couldn't find them.
And then I did something even dumber. Yes, it's possible; I believe I've just proven that saying about stupidity having no limits. I used a database repair function. Yes, now I know: never, ever use a database repair function, they don't actually work! I know that now. I didn't know that then.
So then I backed up (just in case there was anything left that I might want) and uninstalled Drupal, then reinstalled. I don't know if I'll be able to restore anything, but at least now I can start posting things again.
Well, at least not I know a little bit more, right?