WCF / WS-AT Error?

The above error is not related to transactions or WS-AT but indicates a potential contract mismatch from what your client is using and what the service is using.  Can you see if the below samples work better for you?

Transaction samples can be found here (a little deeper in the hierarchy from your link):

http://msdn2.microsoft.com/en-us/library/ms752261.aspx and

http://msdn2.microsoft.com/en-us/library/ms751413.aspx