BuddyPress.org

If you have other plugins that rely on BuddyPress being installed, then this is a bigger project for you than just upgrading BP. Since a lot of the functions and their locations have changed from 1.0 to 1.1, lots of the plugins needed to be upgraded as well.

What I would recommend is deactivating all of your plugins, deactivating BP. Upgrade BP. Make sure everything works okay with just WPMU and BP installed, and then step through each other plugin one by one and upgrade them if they need it, or activate them and see what’s conflicting.