1009 Error Video in Firefox, but not IE

Question

Ok, I am trying to load a video and I get the 1009 error in Firefox, but not in Internet Explorer. I am wondering what is wrong with my code. Please see below. I even tried code from books and get the same error. I have to admit that I am disappointed with the latest version of Flash video.
var myVideo:NetConnection = new NetConnection();
myVideo.connect(null);
var newStream:NetStream = new NetStream(myVideo);
var videoHolder:Video = new Video(720, 480);
stage.addChild(videoHolder);
videoHolder.attachNetStream(newStream);
videoHolder.x = 32;
videoHolder.y = 60;
videoHolder.alpha = 0;
newStream.play("intro.flv");
function fclickV(myevent:MouseEvent):void{
    gotoAndStop(forwardFrame);   
    stage.removeChild(videoHolder);
    my_ns.close()
function bclickV(myevent:MouseEvent):void{
    gotoAndStop(backFrame);   
    stage.removeChild(videoHolder);
    my_ns.close()
forwardV_btn.addEventListener(MouseEvent.CLICK,fclickV);
forwardV_btn.addEventListener(MouseEvent.CLICK,stopSS);
backV_btn.addEventListener(MouseEvent.CLICK,stopSS);
backV_btn.addEventListener(MouseEvent.CLICK,bclickV);

Answer 1

OK, here is the error and here is the correct code. The Error only occurs in Firefox for me, not IE.
TypeError: Error #1009: Cannot access a property or method of a null object reference.
    at tutorial_fla::MainTimeline/frame4()
Updated code
var myVideo:NetConnection = new NetConnection();
myVideo.connect(null);
var newStream:NetStream = new NetStream(myVideo);
var videoHolder:Video = new Video(720, 480);
stage.addChild(videoHolder);
videoHolder.attachNetStream(newStream);
videoHolder.x = 32;
videoHolder.y = 60;
newStream.play("intro.flv");
function fclickV(myevent:MouseEvent):void{
    gotoAndStop(forwardFrame);   
    stage.removeChild(videoHolder);
    newStream.close()
function bclickV(myevent:MouseEvent):void{
    gotoAndStop(backFrame);   
    stage.removeChild(videoHolder);
    newStream.close()
forwardV_btn.addEventListener(MouseEvent.CLICK,fclickV);
backV_btn.addEventListener(MouseEvent.CLICK,stopSS);