Exchange Collaboration Room Calendar - problem sending appointment update

I can successfully initiate appointments in a collaboration room calendar that's connected to Exchange 2003. However, when I go back to an appointment created earlier and try to send an update, it successfully saves the update info in the portal and exchange but fails to send out an update notification like when initiated. Is this how it's supposed to work? In my opinion, everything I send and update it should send an update notification to all attendees. Is this a bug or known problem? What is the solution? Please help.. URGENT. thanks a lot