mi avvicino a actionscript 3 da pochi giorni e non riesco a sbloccare un problema sul preloader che ho aggiunto al file as che ovviamnte racchiudeva un autoresize per la risoluzione e un menu a comparsa .,,
l'errore che mi rimanda e'0 questo , rimanendo su pagina nera

TypeError: Error #1009: Impossibile accedere a una proprietà o a un metodo di un riferimento oggetto null.
at Mainstage/init()
at Mainstage()


il file as e' qeusto:
package
{
import flash.display.MovieClip;
import flash.display.Sprite;
import flash.events.MouseEvent;
import flash.text.TextField;
import flash.events.Event;


public class Mainstage extends MovieClip
{
private var arriveY:int;
public function Mainstage()
{
init();
checkResize();
stage.frameRate=31;
this.addEventListener(Event.ENTER_FRAME,checkProgr ess);
}

private function init():void
{
stage.frameRate=31;

bg_mc.x=0;
bg_mc.y=0;
bg_mc.width=stage.stageWidth;
bg_mc.height=stage.stageHeight;

clip_mc.x=stage.stageWidth/2;
clip_mc.y=stage.stageHeight/2;

rights_txt.x=stage.stageWidth-rights_txt.textWidth;
rights_txt.y=stage.stageHeight-rights_txt.textHeight;
menu_mc.hitArea=hit_area_mc;
hit_area_mc.mouseEnabled=false;

menu_mc.addEventListener(MouseEvent.MOUSE_OVER,set Over);
menu_mc.addEventListener(MouseEvent.MOUSE_OUT,setO ut);
}
private function closeMenu(e:Event):void
{
var dy:Number=arriveY-e.currentTarget.y;
var ay:Number=dy*.2;
e.currentTarget.y+=ay;
if(Math.abs(dy)<=.2)
e.currentTarget.removeEventListener(Event.ENTER_FR AME,closeMenu);
}
private function openMenu(e:Event):void
{
var dy:Number=arriveY-e.currentTarget.y;
var ay:Number=dy*.2;
e.currentTarget.y+=ay;
if(Math.abs(dy)<=.2)
e.currentTarget.removeEventListener(Event.ENTER_FR AME,openMenu);
}


private function setOut(m:MouseEvent):void
{
arriveY=10;
m.currentTarget.removeEventListener(Event.ENTER_FR AME,openMenu);
m.currentTarget.addEventListener(Event.ENTER_FRAME ,closeMenu);
}

private function setOver(m:MouseEvent):void
{
arriveY=98;
m.currentTarget.removeEventListener(Event.ENTER_FR AME,closeMenu);
m.currentTarget.addEventListener(Event.ENTER_FRAME ,openMenu);
}

private function checkResize():void
{
stage.addEventListener(Event.RESIZE, resizeStage);
}

private function resizeStage(event:Event):void
{
init();
}
private function checkProgress(_progress:Event):void
{
var bytes_loaded:Number=_progress.target.loaderInfo.by tesLoaded;
var bytes_total:Number=_progress.target.loaderInfo.byt esTotal;
var percent:Number=Math.round(bytes_loaded/bytes_total*100);
info_txt.text=percent.toString()+' %';
if(percent>=100)
{
this.removeEventListener(Event.ENTER_FRAME,checkPr ogress);
this.gotoAndPlay(2);
lets_go();
}
}

private function lets_go():void
{
trace('ready to start');
}
}
}



qualcuno potrebbe aiutarmi?
grazie
simonetta