Zend_Soap_Client call not working bu service works in plain php

Question

Hi I am trying to use SOAP for the first time. I have searched for and found tutorials that explain it well and I was able to make it work in plain PHP. However building this into my Zend Project brings a problem. Here is a snippet that call the login service. Can anyone help me spot where the error may be? I am running this against a SugarCRM server and I get "SOAP-ERROR: Encoding: object hasn't 'user_name' property "

$client = new Zend_Soap_Client("http://www.example.com/sugar/soap.php?wsdl");
$result_array = $client->login(array('user_auth' => array('user_name' => 'admin','password' => md5('xxxxxxx'),'version' => '0.1'),'application_name' => 'soapleadcapture'));

Thanks