[AS3] Problems with a SWF preloader

This is a preloader.swf source code I’ve been doing…

    import flash.display.*;
    import flash.events.*;
    import flash.net.URLRequest;
    import flash.text.*;

    public class preloader extends Sprite
        private var f:String = "http://www.rockonflash.com/demos/pv3d/macworld/demo/as3/Falcon3D_cameraFollow.swf";
        private var tf:TextField = new TextField();
        private var container:MovieClip;

        public function preloader()

            var loader:Loader = new Loader();
            var container= new MovieClip();

            loader.contentLoaderInfo.addEventListener(ProgressEvent.PROGRESS, onLoadProgress);
            loader.contentLoaderInfo.addEventListener(Event.COMPLETE, completeHandler);
            var request:URLRequest = new URLRequest(f);
        tf.autoSize = TextFieldAutoSize.LEFT;
        tf.textColor = 0xFF0000;
        tf.text = f;
    private function onLoadProgress (event:ProgressEvent):void
        var loaded:int = event.bytesLoaded;
        var total:int = event.bytesTotal;
        var percent:int = loaded/total*100;
        tf.text = "Loading: "+String(percent)+"%";

        private function completeHandler(event:Event):void {
            container = MovieClip(event.target.content); 

It compiles alright, but when it loads the other .swf it gives that error:

TypeError: Error #1009: Cannot access a property or method of a null object reference.
    at Falcon3D_cameraFollow/::init()
    at Falcon3D_cameraFollow$iinit()

Which looks like if isn’t able to initialise the main class of the SWF loaded. Does anyone know what am I doing wrong? What’s the best way to load dinamicly a SWF into another SWF?

Help pleeease! :_(