Probleme variable = 0

hello,
voila j'ai un soucis de variable (AS3).

J'ai le code suivant :

import flash.events.*;

var nbItems:int = 6;
var i:int;
var id:int;
var currentId:Number = 0;

var loader:Loader = new Loader;
loader.contentLoaderInfo.addEventListener(Event.COMPLETE, loaderCompleteHandler);
loader.contentLoaderInfo.addEventListener(IOErrorEvent.IO_ERROR, loadErrorHandler);

function loadErrorHandler(e:Event):void {
    trace("erreur pendant le chargement !");
}

function loaderCompleteHandler(e:Event):void {
    showLoader(false);
    MovieClip(this.parent).gotoAndPlay("off");
    varSeeAll = "down";
   
    MovieClip(this.parent.parent).imgFondShine.gotoAndPlay("off");
    MovieClip(this.parent.parent).cible.addChild(loader);
    MovieClip(this.parent.parent).currentClipRef = loader;
}

function mouseMoveHandler(e:MouseEvent):void {
    MovieClip(this.parent.parent).monSymboleDeLoader.x = stage.mouseX;
    MovieClip(this.parent.parent).monSymboleDeLoader.y = stage.mouseY;
}

for(i=1;i<=nbItems;i++){
    var allBT:SimpleButton = this["b"+i];
    allBT.addEventListener(MouseEvent.CLICK, MouseClick);
    allBT.addEventListener(MouseEvent.MOUSE_OVER, MouseOver);
    allBT.addEventListener(MouseEvent.MOUSE_OUT, MouseOut);
}

function MouseOver(e:MouseEvent){
    id = e.currentTarget.name.substr(1,2);
    if(id != currentId) {
        this["c"+id].gotoAndPlay("on");
        if(id == 1){
            MovieClip(this.parent.parent).imgFondShine.gotoAndPlay("on");
        }
    }
}

function MouseOut(e:MouseEvent){
    if(id != currentId) {
        this["c"+id].gotoAndPlay("off");
        if(id == 1){
            MovieClip(this.parent.parent).imgFondShine.gotoAndPlay("off");
        }
    }
}

function MouseClick(e:MouseEvent){
    if(id != currentId) {
        this["c"+currentId].gotoAndPlay("off");
        currentId = id;
        var url:URLRequest = new URLRequest("anim.swf");   
        loader.load(url);
    }
}


J'ai le message d'erreur suivant :

TypeError: Error #1010: A term is undefined and has no properties.
    at collections01_MODIF_fla::barreBas_7/MouseClick()


Si je change la variable : currentID = 1;

Alors la sa marche mais mon bt1 ne fonctionne pas...


HELP PLZ !!!