PO 7.4 RESTAdapter issue : Unable to parse XML message payload

Dear experts,

We are implementing the scenario Exposing a function module as Restful service with the PO RESTAdapter that's avaiable in PO 7.4 SP09 as described in the blog written by Ivo:

PI REST Adapter – Exposing a function module as RESTful service

When we test the scenario to processing messages the adapter reports the error message:

Error while sending message to module processor: senderChannel '589b39c9b91c3ae99040d9addc6a818b': Catching exception calling messaging system: Unable to parse XML message payload to extract operation for receiver determinationorg.xml.sax.SAXParseException: Premature end of file.

Anyone an idea or solution direction?

Thanks in advance.

Cheers, Luc