bbPress is a popular forum plugin. after finding this article,
http://bbpress.org/forums/topic/forums-not-showing-up/, I'm assuming that the theme is somehow filtering content as one user mentioned.
Unfortunately many themes out there filter the_content and do other weird (and not so correct) things that bbPress doesn?t/can?t take into account.
My recommendation would be to contact the theme author and alert him of the issues you are having.
So here I am. Anyway around this?