I just upgraded to the latest nightly (3.2) build of WordPress and it broke Buddypress.
Every page returned:
Call to undefined method wpdb::WPDB() on FOO/wp-content/plugins/buddypress/bp-forums/bp-forums-bbpress.php line 144
Is something major being deprecated/rewritten in 3.2, or was it perhaps just a bad nightly build?
Thankfully I keep backups, which you should always do when running nightly!