Try resultFormat="e4x"... i.e.:
<mx:HTTPService id="hs" url="
http://somewhere/something.wddx"resultFormat="e4x"
result="handleResult(event)" fault="handleFault(event)" />
<mx:Script>
import mx.rpc.events.FaultEvent;
import mx.rpc.events.ResultEvent;
private var wddxValue:XML;
private function handleResult(event:ResultEvent):void
{
wddxValue = event.result as XML;
}
private function handleFault(event:FaultEvent):void
{
trace("Error: " + event.fault.toString());
}
</mx:Script>