Web services axis

Olá a todos,
estou com um problema ao testar um webservice gerado com Axis.

Segue o código da chamada:

String endpoint = "http://localhost:9082/projeto/services/BolsaValores"; 
	        Service  service = new Service(); 
	        Call     call    = (Call) service.createCall(); 
	        call.setTargetEndpointAddress( new java.net.URL(endpoint) ); 
	        
	        BolsaValoresVO[] array = new BolsaValoresVO[2];
	        x[0].setCodigoString("123");
	        
	        String ret = (String) call.invoke( "alterarBolsaValores",new Object[] { x } );

Ao chamar o metodo "invoke" acontece o seguinte erro:

org.apache.axis.attachments.AttachmentsImpl getAttachmentCount
WARNING: Exception:
AxisFault
faultCode: {http://schemas.xmlsoap.org/soap/envelope/}Server.userException
faultSubcode:
faultString: java.io.IOException: No serializer found for class projeto.vo.BolsaValoresVO in registry org.apache.axis.encoding.TypeMappingDelegate@83a083a
faultActor:
faultNode:
faultDetail:
{http://xml.apache.org/axis/}stackTrace:java.io.IOException: No serializer found for class projeto.vo.BolsaValoresVO in registry org.apache.axis.encoding.TypeMappingDelegate@83a083a
at org.apache.axis.encoding.SerializationContext.serializeActual(SerializationContext.java:1507)

Alguém poderia ajudar?
Grato.