Cross-mailbox Item Move fails - The specified object was not found in the store.

An application is sending an email message to a temporary mailbox and upon successful arrival, moves it to another mailbox's known folder.

* Application used 14.2.51.0 and 14.03.0032.000 Microsoft.Exchange.WebServices.dll.
* Application ran on Exchange Server 2007 SP1 and 2010 SP1.
* Impersonator account is the same for both temporary and final mailboxes.
* The impersonator and the account running the application are the same.
* The account running the application has full access permission on both mailboxes.
* The same scenario works properly via direct EWS, but our preference is to use Managed API.