Error involving xmpp-stanzas while using class.jabber.php to check presence. Any suggestions?

Hi,

I'm trying to use a php script (one of the examples from netflint.net using class.jabber.php) to check the online presence of users. When running the script, it is unable to authenticate, throwing the following error:

----------------------

SEND: <iq type='get' id='auth_e29bb2fc10af16d5509e5d067791c6c7'>
<query xmlns='jabber:iq:auth'>
<username>bot_user</username>
</query>
</iq>

RECV: <iq from='mydomain.com' id='auth_e29bb2fc10af16d5509e5d067791c6c7' type='error'><error code='501' type='cancel'><feature-not-implemented xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/></error></iq>

----------------------

The nearest that I can assume is that it is just what it looks like, and that class.jabber.php is requesting a feature (xmpp-stanzas) that might not be available under ejabberd? Is this correct, or am I missing something altogether (perhaps I need to enable a module that isn't already)? I must admit that I am rather new to jabber server administration, so this could be something really obvious. Any help would be greatly appreciated. Thanks in advance!