Flash CS6 as3 Navigate to URL stops timeline animation!

Hello

I'm hoping someone can help me out! I'm quite new to flash but slowly getting the hang of it. I'm trying to make an interactive banner using jpegs converted to buttons etc with type, all animated. I've got separate layers for everything including mask layers and actions. I just want to navigate on a top layer which is invisible to take the user to a new URL. Everything is working great until I put more than one URL link in the code, as soon as I do the whole banner animation stops!!

If someone could suggest a few ideas it would be much appreciated as I'm all out?!

Many thanks,

here's the code:

import flash.events.MouseEvent;

btn1.addEventListener(MouseEvent.CLICK, btn1Click_1);

btn2.addEventListener(MouseEvent.CLICK, btn2Click_2);

function btn1Click_1(event: MouseEvent): void

{

  navigateToURL(new URLRequest("http://www.google.com"), "_self");

}

function btn2Click_2(event:MouseEvent):void

{

  navigateToURL(new URLRequest("http://www.youtube.com"), "_self");

}

addEventListener(MouseEvent.MOUSE_OVER, mo);

function mo (event:MouseEvent):void

{

event.currentTarget.stop();

}

function mo2 (event:MouseEvent):void

{

event.currentTarget.play();

} addEventListener(MouseEvent.MOUSE_OUT, mo2);