hey i am using the wp-bp-navbar, and its seems to conflict with the theme. What is happening is basically the plugin can generate menus for the admin bar in buddypress. but with the blog mu theme, it seems to create double menus. Doesnot seem to happen with the default theme of buddypress.
here is the link to the plugin
http://buddypress.org/community/groups/add-all-nav-links-to-bp-adminbar/