[johnhiler]

This report sounds similar, although it sounds like they may have been using an earlier RC:

https://bbpress.org/forums/topic/wordpress-mu-271-and-bbpress-10-rc-integration-problem

There was a solution linked from there … hope that points you in the right direction! There was also an integration guide someone created here:

http://umwblogs.org/wiki/index.php/Integrating_WPMu%2C_BuddyPress%2C_and_bbPress

Hope one of those helps!