I've followed the procedure outlined in the Codex under "Giving WordPress Its Own Directory".
From the user's point of view everything's largely working fine. From my point of view as a logged-in user, it's not working fine. I can access WordPress admin as usual, but when it comes to actually browsing the site, I am effectively browsing the site as a logged-out user, because WordPress doesn't seem to realise that I'm actually logged in.
So when maintenance mode is switched on, I get locked out of the site itself (I can still access the admin back-end, no problem). On every page, I have "edit post" links for logged-in users... now I can't see them. Et cetera.
As this is is obviously quite a serious issue, any clues as to how I might resolve this?