[staurand]

Same issue here with BuddyPress 1.2.9 & WP 3.2.1

The problem seems to come from this file :
/buddypress/bp-groups.php
which calls
do_action( 'groups_promoted_member', $user_id, $bp->groups->current_group->id );

before the file below is included
/buddypress/bp-groups/bp-groups-notifications.php
that should add the action to add the notification:
add_action( 'groups_promoted_member', 'groups_notification_promoted_member', 10, 2 );

Quick fix:

function addGroupNotificationFile($user_id, $group_id)
{
require_once ( BP_PLUGIN_DIR . '/bp-groups/bp-groups-notifications.php' );
}
add_action('groups_promoted_member', 'addGroupNotificationFile', 100, 2);