Same result ..
private function listDirectories(event:ResultEvent):void {
var dirs:Array = event.result as Array;
// if the _directories array is null this is our root
request
if(_directories == null) {
_directories = dirs;
}else {
hold.children = dirs;
}
//trace( ObjectUtil.toString(_directories) );
(tree.dataProvider as ArrayCollection).dispatchEvent(new
CollectionEvent(CollectionEvent.COLLECTION_CHANGE));
}

