After the migration of a Microsoft Dynamics CRM 3.0 application to CRM 4.0 and redirecting the BizTalk CRM adapter to the new server we received the following error message from the CRM web service when sending messages:
serializedForm :: Server was unable to process request.
After a few hours of puzzling we found out that this exception was caused by the fact that the send message contained an empty element for a CrmDateTime field. For example:
When the empty CrmDateTime elements where removed from the message everything runs smoothly again.