Menu animation not stopping and submenu not showing

Hello,

I would be most grateful of your help.  I'm working on a project for my students, using CS6, AS3 and we are to create a basic button navigation with a submenu.  My problem is that the animation won't stop at the given keyframes and just runs on.  The submenu doesn't show up either.  Thanks in advance for your help.

Here is the AS3 code:

import fl.transitions.Tween;

import fl.transitions.easing.*;

import flash.events.MouseEvent;

var scene:String="";

var submenuVisible:Boolean=false;

var myTweenAlpha:Tween;

submenu.mouseEnabled=false;

submenu.mouseChildren=false;

stop();

btn_home.addEventListener(MouseEvent.CLICK, NavigateHome);

function NavigateHome(event:MouseEvent):void

{

  scene="Home";

  submenuVisible=false;

  CheckSubmenu();

  play()

}

btn_subjects.addEventListener(MouseEvent.CLICK, NavigateSubjects);

function NavigateSubjects (event:MouseEvent):void

{

  scene="Subjects";

  submenuVisible=true;

  CheckSubmenu();

  play();

}

btn_about.addEventListener(MouseEvent.CLICK, NavigateAbout);

function NavigateAbout(event:MouseEvent):void

{

  scene="About";

  submenuVisible=false;

  CheckSubmenu();

  play();

}

btn_enquiry.addEventListener(MouseEvent.CLICK, NavigateEnquiry);

function NavigateEnquiry (event:MouseEvent):void

{

  scene="Enquiry";

  submenuVisible=false;

  CheckSubmenu();

  play();

}

function CheckSubmenu():void

{

  if (submenuVisible==true)

  {

  myTweenAlpha= new Tween(submenu, "alpha",

Strong.easeInOut, submenu.alpha, 1, 1.5, true);

  submenu.mouseEnabled=true;

  submenu.mouseChildren=true;

  }

  else if (submenuVisible==false)

  {

  myTweenAlpha= new Tween(submenu, "alpha",

Strong.easeInOut, submenu.alpha, 0, 1.5, true);

  submenu.mouseEnabled=false;

  submenu.mouseChildren=false;

  }

}

submenu.btn_subject1.addEventListener(MouseEvent.CLICK),

NavigateSubject1);

function NavigateSubject1 (event:MouseEvent):void

{

  scene="Subject1";

  play();

}

submenu.btnsubject2.addEventListener(MouseEvent.CLICK

NavigateSubject2);

function NavigateSubject2 (event:MouseEvent):void

{

  scene="Subject2";

  play();

}

submenu.btn_subject3.addEventListener(MouseEvent.CLICK,

NavigateSubject3);

function NavigateSubject3 (event:MouseEvent):void

{

  scene="Subject3";

  play();

}

submenu.btn_subject4.addEventListener(MouseEvent.CLICK,

NavigateSubject4);

function NavigateSubject4 (event:MouseEvent):void

{

  scene="Subject4";

  play()

}

submenu.btn_subject5.addEventListener(MouseEvent.CLICK,

NavigateSubject5);

function NavigateSubject5 (event:MouseEvent):void

{

  scene="Subject5";

  play();

}