In the middle of a session yesterday I got the login screen for the forums. I had already been logged in and was already reading posts, but I tried signing in again, anyway. It didn't work. Tried multiple times over the next half day. I was convinced the forums were down.
Tried just now with Safari (rather than Firefox) and it worked, but only after giving me a too-many-redirects error on the first attempt. I'm in now with Safari. Still can't get in with Firefox.