Consider the following scenario. As a delegate in a Microsoft Exchange Server 2007 environment, you create, send, and then update meeting requests for the organizer by using Exchange Web Service (EWS). However, the operation does not work if the delegate tries to cancel a meeting, and then tries to send the cancellation update request for the organizer by using EWS. In this scenario, when the delegate tries to cancel a meeting for the organizer, an "ErrorItemNotFound" error is returned.
To resolve this problem, install the following update rollup:
971534 Description of Update Rollup 1 for Exchange Server 2007 Service Pack 2
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.