I'm using this AS3 code to open popover window:

Code:
//facebook button// 
fbBtn.addEventListener(MouseEvent.CLICK, fb);  function fb(Event:MouseEvent):void{
ExternalInterface.call("window.open", "https://www.facebook.com/pages/Voiceguy1-Communications-Voiceovers-by-Chris-Mezzolesta/105793199443085?fref=ts", "win", "height=559,width=1000,toolbar=no,scrollbars=yes", "_blank");  }
It works great in Chrome. In Safari it takes a long time (30-60 seconds) to work. In Firefox it gives me this error message:

Warning: Unresponsive script A script on this page may be busy, or it may have stopped responding. You can stop the script now, or you can continue to see if the script will complete. Script: http://chrisvoiceover.com/:16

but still opens the popover, only it opens behind the browser.

Help?