I keep getting the below error only in firefox

ArgumentError: Error #1063: Argument count mismatch on com.flashden::MenuItem(). Expected 1, got 0. at flash.display::Sprite/constructChildren() at flash.display::Sprite() at flash.display::MovieClip() at com.flashden::Preview()

Below is my menu script:

package com.flashden { import flash.display.MovieClip; import flash.text.; import flash.events.MouseEvent; import flash.events.; import flash.net.URLRequest; import flash.display.Loader;

public class MenuItem extends MovieClip { private var scope; public var closedX :Number

public static const OPEN_MENU = "openMenu"; function callLink(event:MouseEvent):void { public function MenuItem(scope) { // set scope to talk back to -------------------------------// this.scope = scope;

// disable all items not to be clickable -------------------// txt_label.mouseEnabled = false; menuItemShine.mouseEnabled = false; menuItemArrow.mouseEnabled = false;

// make background clip the item to be clicked (button) ----// menuItemBG.buttonMode = true;

// add click event listener to the header background -------// menuItemBG.addEventListener(MouseEvent.CLICK, clickHandler); }

private function clickHandler (e:MouseEvent) { scope.openMenuItem(this); }

public function loadContent (contentURL:String) { var loader:Loader = new Loader(); configureListeners(loader.contentLoaderInfo);

        var request:URLRequest = new URLRequest(contentURL);
        loader.load(request);

// place x position of content at the bottom of the header so the top is not cut off ----// loader.x = 35;

// we add the content at level 1, because the background clip is at level 0 ----// addChildAt(loader, 0); }

private function configureListeners(dispatcher:IEventDispatcher):void { dispatcher.addEventListener(Event.COMPLETE, completeHandler); dispatcher.addEventListener(HTTPStatusEvent.HTTP_STATUS, httpStatusHandler); dispatcher.addEventListener(Event.INIT, initHandler); dispatcher.addEventListener(IOErrorEvent.IO_ERROR, ioErrorHandler); dispatcher.addEventListener(Event.OPEN, openHandler); dispatcher.addEventListener(ProgressEvent.PROGRESS, progressHandler); dispatcher.addEventListener(Event.UNLOAD, unLoadHandler); }

    private function completeHandler(event:Event):void {
        //trace("completeHandler: " + event);

// remove loader animation ----------------// removeChild(getChildByName("mc_preloader")); }

    private function httpStatusHandler(event:HTTPStatusEvent):void {
       // trace("httpStatusHandler: " + event);
    }

    private function initHandler(event:Event):void {
        //trace("initHandler: " + event);
    }

    private function ioErrorHandler(event:IOErrorEvent):void {
        //trace("ioErrorHandler: " + event);
    }

    private function openHandler(event:Event):void {
        //trace("openHandler: " + event);
    }

    private function progressHandler(event:ProgressEvent):void {
        //trace("progressHandler: bytesLoaded=" + event.bytesLoaded + " bytesTotal=" + event.bytesTotal);
    }

    private function unLoadHandler(event:Event):void {
        //trace("unLoadHandler: " + event);
    }     

} }

Any idea why this is happening?