Deleting Outlook 2007 meeting update notification causes same meeting request to be sent out to all

We are running Exchange 2003 SP2 with Outlook 2007 client. When a delegate creates a meeting requestion on behalf or an organizer and sends it out to all staffs. Everyone receives the meeting request and either accepts or decline. The organizer will then get a blue icon with an "i" on it showing up on his inbox. Whenever he moves or delete this message, it will cause the meeting request to go out to all staffs again. Exact same meeting request. Also, we have Iphone in our environment. Any help from anyone would greatly be appreciated.