I think I can help ....this happened to me and all you need to do is:
go back to the main forum page,
at top right re-type in your username and password THEN click on LOGIN (even though you appear as if you are already logged in). THEN click on chat.
You can go into the forums and browse the topics without plugging that info in...but apparently when you go to chat (or edit posts) it requires this info be typed in (not sure why, but that's what I discovered).
Anyway, hope this is helpful!