loadXML only works with Alert() command included ... CRAZY!?

Okay, here is the code snippet that is causing problems ...

var xmlDoc;
var browser;
function loadXML()
{
// code for IE
if (window.ActiveXObject)
{
xmlDoc=new ActiveXObject("Microsoft.XMLDOM");
xmlDoc.async=false;
xmlDoc.load("INCLUDE_XML_ChannelLineUp.xml");
browser = "ie";
//displayPackage("America's Top 100","AT100",'','','','AT100');
}
// code for Mozilla, Firefox, Opera, etc.
else if (document.implementation && document.implementation.createDocument)
{
xmlDoc=document.implementation.createDocument("","",null);
xmlDoc.load("INCLUDE_XML_ChannelLineUp.xml");
//displayPackage("America's Top 100","AT100",'','','','AT100');
browser="ff";
alert("Your channels are loading. Press ok to continue.");

}
else
{
alert('Your browser cannot handle this script');
}
}

The script appears on this page (amongst others): http://www.satellitesolutions.com/di...pkgs_at100.asp

In this conditional section "// code for Mozilla, Firefox, Opera, etc.", if I remove the Alert() command, the function does not work properly. It makes no sense to me. With the alert command the FF user must press "ok" and then the channels load. The IE user does not get the prompt, and everything works fine.

Am I executing out of order? Is the Alert() returning some strange required value for the FF user?

Please help.

Thanks,
David