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