--- /buddypress/bp-groups.php (BP 1.2.6)	Thu Oct 21 13:58:22 2010
+++ /buddypress/bp-groups.php (working copy)	Thu Nov 11 13:04:07 2010
@@ -1374,7 +1374,6 @@
 function groups_update_last_activity( $group_id ) {
 	groups_update_groupmeta( $group_id, 'last_activity', gmdate( "Y-m-d H:i:s" ) );
 }
-add_action( 'groups_joined_group', 'groups_update_last_activity' );
 add_action( 'groups_leave_group', 'groups_update_last_activity' );
 add_action( 'groups_created_group', 'groups_update_last_activity' );
 add_action( 'groups_new_forum_topic', 'groups_update_last_activity' );