The online users are not properly displayed.
Line 186 is:
$user_access = db_query("SELECT timestamp FROM {sessions} WHERE uid = :uid", array(':uid' => $uid))->fetchField();
but as stated in http://drupal.org/node/36822 it should be
$user_access = db_query("SELECT MAX(timestamp) FROM {sessions} WHERE uid = :uid", array(':uid' => $uid))->fetchField();