proxy->operation ( $payload_structure) doesn't appear to create payload correctly

Greetings all, I'm using WSClient in WSDL mode. I've run wsdl2php on the wsdl in question and the include works fine (file attached).

I create the client (I have my client wrapped up inside another object just to take care of some setup housekeeping types of things):

$this->client = new WSClient( array (      'wsdl'          => $this->local_wsdl_file,

'policy'        => $this->WSPolicy,

                                                                                'securityToken' => $this->UsernameToken,

                                                                                'classmap'      => $this->class_map,

                                                                                )

                                                                );

$this->proxy = $this->client->getProxy();

I then create the data structure and call the proxy:

$operation = "CI_MESSAGE_CATALOG_CI_G";

$struct = new Get__CompIntfc__MESSAGE_CATALOG_CI;

$struct->MESSAGE_SET_NBR = 3;

$response = $this->proxy->$operation ( $struct );

The call runs but the target server returns an unexpected error and after tracing the traffic it appears that MESSAGE_SET_NBR is being set to nil rather than to 3 prior to the data being sent. 

I set the log level to debug and attached the pertinent wsf_php_client.log snippet. 

Help please!!  J  Thanks.