XML over MSMQ

Hi
I've a strange problem with MSMQ:
From Navision I send a xmlDoc to the MSMQ, which seems to work quite well.

On the other side is a webservice (ASP.NET) which should read the MessageQueue:

Dim inMsg As System.Messaging.Message
Dim queueFromNavi As New MessageQueue(".\Private$\fromnavi")
Dim XmlDocument As New XmlDocument
queueFromNavi.Formatter = New XmlMessageFormatter(New Type() {GetType(XmlDocument)})
inMsg = queueFromNavi.Receive()
Dim xmlDocument2 As New XmlDocument
xmlDocument2 = inMsg.Body

We get the ffw errror msg...
System.InvalidOperationException: Cannot deserialize the message passed as an argument. Cannot recognize the serialization format. at System.Messaging.XmlMessageFormatter.Read...

Any ideas? Thank you in advance
Thomas