problem aligning images in slideshow

I have a slide show in a site I'm building for a friend the slide show can be viewed by going to http://www.droolpigs.com/   and clicking the About Us button

the inages are supposed to be centered and 90% of the time they are.  I would like to see them centered 100% of the time.

here's the code:

        import com.greensock.*;
         import com.greensock.easing.*;
        import flash.display.*;
        import flash.utils.*;
        import flash.events.*;
        import flash.net.*;
        import flash.text.*;

        var myFont:Font3 = new Font3();
        var extReq:URLRequest = new URLRequest("bio.txt");
        var extLoader:URLLoader = new URLLoader();
        var myFormat:TextFormat = new TextFormat();
///       
        var tf:TextField = new TextField();
        var tf3:TextField = new TextField();
        var msk:Sprite = new Sprite();
        var tl:TimelineMax = new TimelineMax({repeat:-1});   
///
//        var bio:Bio = new Bio();
         var bars:Bars = new Bars();
        var n:int = 0;
        var intCurrentSlide:int;
        var req:URLRequest;
           var holder:Sprite = new Sprite();
//        var holderBG:HolderBG = new HolderBG();
        var loader:Loader;
        var rand:int;
        var nxtNum:int;
        var picNum:String;
        var slideCount:int;
        var xmlLoader:URLLoader;   // slideshow xml loader
        var xmlSlideshow:XML;  // slideshow xml
        var strXMLPath:String = "bioPics-data.xml";
        var slideName:String;
       var history:Array = new Array();
         var duration:Number=.5;
        var prevSlide:String;
        var timeline:TimelineMax;
//////////      

        xmlLoader = new URLLoader();  
        xmlLoader.addEventListener(Event.COMPLETE, onXMLLoadComplete);
        xmlLoader.load(new URLRequest(strXMLPath));
       
///////////// text setup ////////////////////
tf.x =-285;
//tf.y =655;
tf.y=700;
tf.width = 700;
tf.height = 800;
tf.multiline=true;
tf.wordWrap=true;
tf.condenseWhite=true;

//tf2

tf3.x =-285;
tf3.y =660;
tf3.width = 700;
tf3.height = 20;
tf3.htmlText = '<font color = "#dd8800" size = "14px">Contact links and Email:      <a href="http://www.droolpigs.com">droolpigs.com</a> | <a href="http://www.myspace.com/acousticshadowz">myspace site</a>      <a href="mailto://droolpigs@gmail.com">droolpigs@gmail.com</a> | <a href="mailto://invisibleblindman@hotmail.com">invisibleblindman@hotmail.com</a></font>';

addChild(tf);
addChild(tf3);

msk.graphics.beginFill(0x000000);
msk.graphics.drawRect(0, 0, 700, 165);
msk.x = -285;
msk.y = 485;
msk.graphics.endFill();

extLoader.addEventListener(Event.COMPLETE, textReady);

myFormat.font = myFont.fontName;
myFormat.color = "0xffaa00";
//0x77ffaa

myFormat.size = 18;
myFormat.leading = 2.5;

tf.defaultTextFormat=myFormat;
tf.embedFonts=true;
tf.alpha=1;

extLoader.load(extReq);

function textReady(e:Event):void {
    tf.cacheAsBitmap=true;
     msk.cacheAsBitmap=true;
    tf.mask=msk;
    addChild(msk);
    tf.htmlText=e.target.data;
}

tl.insert( new TweenLite(tf, 70, {y:"-940", ease:Linear.easeNone}) );
//////////////text setup////////////////////////   
       
            createTimeline();
                
        function onXMLLoadComplete(e:Event):void {
             xmlLoader.removeEventListener(Event.COMPLETE, onXMLLoadComplete);
             xmlSlideshow = new XML(e.target.data);     // create new xml with the received data
             slideCount = xmlSlideshow..image.length();   // get total slide count
             loadSlide();
        }

         function loadSlide():void {
              prevSlide=history[history.length-1];
            rand = Math.ceil(Math.random()* slideCount - 1); 
             loader = new Loader();
             req = new URLRequest(xmlSlideshow..@src[rand]);
             loader.contentLoaderInfo.addEventListener(Event.COMPLETE, displaySlide);
             loader.load(req);
            slideName = xmlSlideshow..@src[rand].toString();
           
        if(slideName != prevSlide){
                 history.push(slideName);
                loader.load(new URLRequest(xmlSlideshow..@src[rand]));
               
            }else{
                loadSlide();
                }
        }

        function createTimeline():void{
        timeline =new TimelineMax({repeat:1,repeatDelay:5,yoyo:true,onComplete:loadSlide, paused:true});
        for (var count:int = 1; count <=10; count++) {
            var mc:MovieClip=bars["bar"+count];
            timeline.append(TweenMax.from(mc, duration, {x:"64", alpha:0, ease:Cubic.easeOut}), -.4);
             }
        }

        function displaySlide(e:Event = null):void {
            loader.contentLoaderInfo.removeEventListener(Event.COMPLETE, displaySlide);
            if (holderBG.holder)
            {
            holderBG.removeChild(holder);
            holderBG.holder = null;
            }
//            trace ("holder.numChildren "+holder.numChildren);
             if(holder.numChildren > 0){holder.removeChildAt(0);}
              holder.addChild(loader.content);
           
            // center the pic
            holder.x=holderBG.width/2 - holder.width/2;
            holder.y=holderBG.height/2 - holder.height/2;
            // make the mask position over the pic
             bars.x=holder.x;
             bars.y=holder.y;
              bars.cacheAsBitmap=true;
              holder.cacheAsBitmap=true;
             holder.mask=bars;
             bars.width = holder.width;
              bars.height = holder.height;
             holderBG.addChild(holder);
              holderBG.addChild(bars);
            timeline.restart();        }