duplicate messages from MSMQ

Hi,

We have MS BizTalk Server 2006 R1 installed with SQL Server 2005 Service Pack 3.

We have 5000 messages stored in a transactional queue in MSMQ. We have a BizTalk Receive Port enabled on this queue (using the MSMQ adaptor to retrieve the messages). In the MSMQ Transport Properties on the Receive port we have Batch Size = 1, Ordered Processing = False, Transactional = True. The Receive Handler for the receive port is MSMQ_Receive (we created a seperate host instance for the MSMQ adaptor) . We then have a File send port which is subscribed to our MSMQ receive port. In the File send port we have Ordered Delivery = False.

The 5000 messages are successfully extracted from the queue, however we get 5005 messages in our folder on the file system (this varies – sometimes we get 5005, sometimes 5010 etc. but never 5000 exactly!) – so there are duplicates. Has anyone experienced this problem before or have any advice on how to fix it?

Thanks,
Ian