Hi Jim,
It is a known bug of powerbuilder during webservice proxies generation.
Powerbuilder does not recognize inheritance between objects from the wsdl.
The solution is to edit the source of the generated proxies and replace the "nonvisualobject" ancestor class by the real ancestor class in the first line.
I had this kind of bug while consuming webservices with Salesforces.
In Salesfoces, the ancestor of all objects is "sObject". Replacing "nonvisualobject" by "sObject" in all proxies that you will use should correct the problem.
EX:
global type sf_ApexLog from nonvisualobject
must be changed in
global type sf_ApexLog from sObject
Of course, dont change the proxy of the ancestor (here sObject).