Well, that'll teach me to go for long lunches. It seems that while I was out of the way someone who shouldn't have had the permissions to do so made the mistake of doing something to the root of the development server. If you go to the actual drive, you can see that this hasn't actually deleted any of the files or anything but it has fooled FrontPage into thinking they're not there, causing something of a panic as you can imagine. So now I have to bully FrontPage. Oh what fun. And amend the permissions.
Addendum: Ah-ha. They changed the IIS settings so that the default web was pointing somewhere else. They actually got someone in the web-server team, who really should have known better, to do it for them. Honestly.