Encontre la solución al problema, lo copio aqui por si le sirve a alguien mas.
ActionScript Code:
YAHOO_button.addEventListener(MouseEvent.CLICK,cli ckHandler1);
function clickHandler1(event:MouseEvent):void{
navigateToURL(new URLRequest("
http://www.yahoo.com"));
}
HOTMAIL_button.addEventListener(MouseEvent.CLICK, clickHandler2);
function clickHandler2(event:MouseEvent):void {
var req:URLRequest = new URLRequest("
http://www.hotmail.com"));
navigateToURL(req, "_blank");
}
GMAIL_button.addEventListener(MouseEvent.CLICK, clickHandler3);
function clickHandler3(event:MouseEvent):void {
var req:URLRequest = new URLRequest("
http://www.gmail.com"));
navigateToURL(req, "_blank");
}