On the plus side, I am one of the admins on testbp. It’s probably because bbPress 2.0 tries to use “forums”, and BuddyPress also tries to use “forums”. BuddyPress must be winning.
Try going to wp-admin > Settings > Forums, and set the “Forums base” and “Topics base”. There’s also a page called “discussion”. I’ve not used bbPress 2.0, so I’m not really sure. @johnjamesjacoby will know!