I have the same problem and i found this:
http://forums.oscommerce.nl/index.php?showtopic=17708
change in /includes/classes/message_stack.php
goto "function add_session..." and change $messageToStack = array(); in //$messageToStack = array(); $_SESSION['messageToStack'] = array(); and change: $messageToStack[] = array('class' => $class, 'text' => $message, 'type' => $type); in: // $messageToStack[] = array('class' => $class, 'text' => $message, 'type' => $type); $_SESSION['messageToStack'][] = array('class' => $class, 'text' => $message, 'type' => $type);
this works perfekt with OSC v2.2 RC2
( I see this also http://www.oscommerce.com/forums/topic/387479-messagestack-and-add-session/ , but this works NOT in my shop... )