Flash error pop-up when animation playing (ie)

Buongiorno a tutti !

Let's start by saying I'm a beginner. Still, I've made it making a "simple" fl cs4 animation. Here the html page: http://www.under21pro.com/site/flash/onRelease02.html

It seems to be working fine with firefox and chrome, but if you open it with internet explorer you'll get a pop-up (after about 10 sec when the animation goes back to the start) with a error message.
There's also a little problem with opera: the pointer doesn't change when you mouse over.

Here's the only script I'm using:

clickMe.addEventListener(MouseEvent.MOUSE_DOWN, mouseDownHandler);
function mouseDownHandler(event:MouseEvent):void {
     navigateToURL(new URLRequest("http://..."));
}

Does anybody know where the error comes from ?

Thanks allot for checking this out !