Problem loading upload list in Firefox (Java applet)

<script language="javascript" src="iuembed.js"></script>
<script language="javascript">
var iu = new ImageUploaderWriter("ImageUploader", 650, 450);

...

iu.activeXControlEnabled = true;
iu.javaAppletEnabled = true;

....


iu.fullPageLoadListenerName = "fullPageLoad";

function fullPageLoad(){
       uploader = getImageUploader('ImageUploader');

	try
	{
		uploader.LoadUploadList(1);
	} 
	catch (e) 
	{
		alert("An exception occurred in fullPageLoad(). Error name: " + e.name 
		+ ". Error message: " + e.message); 
	}
	alert("Loaded");    
}

// functions to switch between Thumbnail and Full Image modes.
function UploadThumbnails() {
	uploader = getImageUploader('ImageUploader');

	try
	{
		uploader.LoadUploadList(1);
	} 
	catch (e) 
	{
		alert("An exception occurred in UploadThumbnails(). Error name: " + e.name 
		+ ". Error message: " + e.message); 
	}

	uploader.setAction("<%= basePath %>ThumbnailUpload");
	uploader.setUploadThumbnail1FitMode("Width"); 
	uploader.setUploadSourceFile("false");
	// set custom POST field so server knows we're uploading thumbnails
	uploader.AddField("UploadType", "thumbnail");
	uploader.Send();
	return false;
}

</script>

<input type="button" onclick="UploadThumbnails()" value="Upload Thumbnails" />