xml interop error 51

 I'm getting this error when trying to use xml interop 

<jdeResponse environment="default" type="default" user="default" session="default">

<errorReport code="51" state="1">

Document could not be recognized

</errorReport>

</jdeResponse>

here is the xml in file

<?xml version='1.0' encoding='utf-8' ?>

<jdeRequest type='callmethod' user='' pwd='' environment='JTR910' session='' sessionidle=''>

<callMethod name='GetEffectiveAddress' app='P01012' runOnError='no'>

<params>

<param name='mnAddressNumber'>322791</param>

</params>

</callMethod>

</jdeRequest>

I'm using the testdriver class found here

E1: XML: TestDriver.java for 8.98 and above. Setup and configuration. - Windows and Unix [ID 652925.1]