/me smells bug. O:-)
In ProfileOptions.controller.php:
require_once(SUBSDIR . '/ProfileOptions.subs.php');
$buddiesArray = getBuddiesID($new_buddies);
// Now update the current users buddy list.
$user_profile[$this->_memID]['buddy_list'] = implode(',', $buddiesArray);
require_once(SUBSDIR . '/ProfileOptions.subs.php');
$new_buddiesArray = getBuddiesID($new_buddies);
$old_buddiesArray = explode(',', $user_profile[$this->_memID]['buddy_list']);
// Now update the current users buddy list.
$user_profile[$this->_memID]['buddy_list'] = implode(',', array_unique(array_merge($new_buddiesArray, $old_buddiesArray)));