PropertyCollector.retrieveProperties question

Hi there

I'm trying to get rootFolder property of the ConversionManager (http://www.vmware.com/support/developer/converter-sdk/conv43_apireference/converter.server.conversion.ConversionManager.html), and here is my code (Java):

     
     ManagedObjectReference pCollector = getServiceContent().getPropertyCollector();
          
     //get rootFolder of ConverterServerConversionConversionManager
     ManagedObjectReference convManager = getServiceContent().getConversionManager();
     ObjectSpec os = new ObjectSpec();
     os.setObj(convManager);
     os.setSkip(false);
     os.getSelectSet();
          
     PropertySpec pSpec = new PropertySpec();
     pSpec.setAll(true);
     pSpec.setType(convManager.getType());
     pSpec.getPathSet().add("rootFolder");
          
     PropertyFilterSpec pfss = new PropertyFilterSpec();
     pfss.getObjectSet().add(os);
     pfss.getPropSet().add(pSpec);
     
     List<ObjectContent> result = getPort().retrieveProperties(pCollector, Arrays.asList(pfss));

The retrieveProperties call is executed without errors,  but as the result I get the list of single ObjectContent wich has all its properties == null

What's wrong with the code above? I'm using Converter 4.3