Very weird - I posted on a thread around 10.30 last night, closed the page but didn't log out. A couple of hours later opened the site again, it took ages to load, and I was logged out. Made multiple attempts to log in but only got a page with the message "Sorry, we're not accepting any new registrations at the moment, you're welcome to stay and browse" or words to that effect.
Eventually quite a while later I was able to get to the login page and get in.
I've had a quick look to see if anyone else mentioned this but can't see anything.
Hope it was just a technical hitch and not the result of a cyber attack or whatever.