I wonder is this a buddypress problem or a theme problem? I'm using buddypress 1.1.2 and corporate theme 1.3. I enabled group discussion in admin of a group, after that I created a test discussion, but all I could see was an error says "There was an error when creating the topic." So I couldn't create any topic.
How the forum was installed? I'm not using an existing bbpress forum, but I'm using the integrated bbpress forum with one click install from within Buddypress 1.1.2.