I hope this is the right forum to report bugs.
A few hours ago, I set up a new Beta 2 forum, and the first thing I did was to put the forum into maintenance mode. Forum worked fine while I was logged in, I was able to change all the settings and everything you'd expect an admin to be able to do...
Then I logged out. The forum completed the sign out sequence but instead of showing me the maintenance message, Firefox told me the forum was endlessly looping.
This continued on all browsers and even on my other computer, so I was sure this wasn't a Firefox issue... and it kept going until I FTP'd in and turned off the maintenance mode manually, then the forum worked perfectly again and I was able to log back in.