Regardless of my cookie settings in IE, whenever I open a page via "window.showModalDialog" that uses a "tokenized" service I get the below pop-up:

If I use "window.open" instead, the issue is not present. This prompt occurs for each feature layer that I use, so for my app I have 24 prompts (24 layers), which is just not acceptable. Is there some parameter I can pass during the instantiation of the layer that will prevent this?
Below is some sample code that shows the issue:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<title></title>
</head>
<body>
<button onclick="myFunction()">Copy Text</button>
</body>
<script>
function myFunction()
{
window.showModalDialog('http://developers.arcgis.com/javascript/samples/layers_label/', '0', 'resizable:1;dialogHeight:' + 600+ 'px;dialogWidth:' + 800+ 'px');
}
</script>
</html>