1136 incorrect number of arguments. expected 0

package  {

          import flash.display.MovieClip;

          import flash.utils.Timer;

          import flash.events.Event;

          import flash.net.URLLoader;

          import flash.net.URLRequest;

          import flash.events.*;

          import flash.events.TimerEvent;

          public class JuteBox extends MovieClip {

                    private var tracks:Array;

                    private var i:int=0;          //points to current track

                    private var pollTimer:Timer = new Timer(100);          //updates UI periodically

                    public function JuteBox(url:String="content/playList.xml") {

                              trace( "JuteBox" );

                              //load the playList

                              var loader = new URLLoader();

                              loader.load( new URLRequest(url));

                              loader.addEventListener( Event.COMPLETE, onListLoaded );

                              //set up the timer

                              pollTimer.addEventListener(TimerEvent.TIMER, updateUI );

                              pollTimer.start();

                              //initizlize the interface

                              //buttons

                              play_btn.addEventListener( MouseEvent.CLICK,

                                        function (e) { tracks.play() }

                                        );

                              //sliders

                              //text box

                              // constructor code

                    }//con

                    private function onListLoaded(e:Event):void {

                              trace( "onListLoaded");

                              var loader = e.target;

                              //populate the array tracks

                              var playList = new XML( loader.data );

                              trace( playList.Song );

                              tracks = [];

                              for each (var song in playList.Song) {

                                        tracks.push( new Track ( song.@src ));

                              }

                    }//onbListLoaded

                    //updates the interface perdically

                    private function updateUI(e:Event=null):void {

                    }//updateui

                    //advances to next track

                    private function next(e:Event=null):void {

                    }//next

                    //goes to previous track

                    private function prev(e:Event=null):void {

                    }//prev

          }//class

}//pack

I'm sure it is something obvious but I can't find it.