XML Loader Class returns NULL In Flash

So I dived into AS3 and decided to create an XML Loader class.


package
{

    import flash.events.Event;
    import flash.net.URLLoader;
    import flash.net.URLRequest;
    import flash.xml.*;
    import flash.events.IOErrorEvent;
  
    public class XMLLoader {
        
        public var myXML:XML;    
        private var loader:URLLoader;

        public function XMLLoader(dataPath) 
        {
            var request:URLRequest = new URLRequest(dataPath);

            loader = new URLLoader();
            
            try 
            {
                loader.load(request);
            }
            catch (error:SecurityError)
            {
                trace("A SecurityError has occurred.");
            }

            loader.addEventListener(IOErrorEvent.IO_ERROR, errorHandler);
            loader.addEventListener(Event.COMPLETE, loaderComplete);
        }

        private function loaderComplete(event:Event):void 
        {
            try
            {
                myXML = new XML(loader.data);
                //trace(myXML);
            }
            catch (e:TypeError)
            {
                trace("Could not parse the XML file.");
            }
        }

        private function errorHandler(e:IOErrorEvent):void
        {
            trace("Had problem loading the XML File.");
        }
    }
}

When I run the trace statement from within the class the XML returns fine.
In Flash I instantiate the XMLLoader class and try to trace a property of the object…


// XML filepath
var myXMLPath = "q_sets/";
// Instanciate set list object
var mySetList:XMLLoader = new XMLLoader(myXMLPath + "qset_admin.xml");

trace(mySetList.myXML.descendants("qset_0").toXMLString());

When I test this I receive the error below:

TypeError: Error #1009: Cannot access a property or method of a null object reference.
at cs_quiz_fla::MainTimeline/frame1()

Anyone have any ideas what might be happening?
Thanks in advance for any help with this one.