The top bar shows "Log in or Create an account" but I'm able to see my user icon in the Forum Preferences, and I'm able to post in the forums as if I were logged in. I didn't log out the last time I visited the forums, and there's no Log out button now.
Clicking "MY ACCOUNT" brings me to the login page as expected.
Did you clear your cookies after the forum upgrade? A lot of info is stored in it, and probably isn't consistent with the new setup.