Con il pannello crei il binding solo con i components: risolvi facendo a manina via script..
codice:
// supponendo che il WebServiceConnector si chiami "connector"
import mx.data.binding.EndPoint
import mx.data.binding.Binding
var srcEndPoint:EndPoint = new EndPoint();
var endEndPoint:EndPoint = new EndPoint();
srcEndPoint.component = connector;
srcEndPoint.property = "results";
srcEndPoint.event = "result";
endEndPoint.component = casella_txt;
endEndPoint.property = "text";
var listToDesc:Binding = new Binding(srcEndPoint, endEndPoint);
connector.trigger();