IU fails on WinXP and IE7, but not FF

//<![CDATA[
//Create JavaScript object that will embed Image Uploader to the page.
var iu = new ImageUploaderWriter("ImageUploader1", 620, 400);

//For ActiveX control full path to CAB file (including file name) should be specified.
iu.activeXControlCodeBase = "../ImageUploader4.cab";
iu.activeXControlVersion = "4,5,50,0";
iu.activeXControlEnabled=false;


//For Java applet only path to directory with JAR files should be specified (without file name).
iu.javaAppletCodeBase = "./"; // the applet is in the same directory as the file
iu.javaAppletCached = false;
iu.javaAppletVersion = "2.5.50.0";

//Configure user quota restriction. In real-life application these values should be 
//loaded from server.
iu.addParam("MaxFileCount", "6");
iu.addParam("MaxTotalFileSize", "50331648");

iu.showNonemptyResponse = "off";

//Configure appearance and behaviour.
iu.addParam("PaneLayout", "TwoPanes");
iu.addParam("TreePaneWidth", "205");
iu.addParam("ShowButtons", "False");
iu.addParam("ShowDebugWindow", "true");

//Configure colors.
iu.addParam("BackgroundColor", "#006B95");
iu.addParam("SplitterLineColor", "#0066cc");

//Configure border and splitter line style.
iu.addParam("FolderPaneBorderStyle", "None"); //NOT SUPPORTED IN JAVA
iu.addParam("UploadPaneBorderStyle", "None"); //NOT SUPPORTED IN JAVA
iu.addParam("TreePaneBorderStyle", "None"); //NOT SUPPORTED IN JAVA
iu.addParam("SplitterLineStyle", "Dot"); //NOT SUPPORTED IN JAVA

//Configure Image Uploader to rotate photos automatically 
//according to the orientation stored in EXIF metadata.
iu.addParam("AllowAutoRotate", "true");

//Configure file mask to upload JPEG and TIFF images only.
iu.addParam("FileMask", "*.jpeg;*.jpg;*.jpe;*.tif;*.tiff");

//Set image size restrictions.
iu.addParam("MinImageWidth", "360");
iu.addParam("MinImageHeight", "360");

//Set image filesize restrictions.
iu.addParam("MaxFileSize", "8388608");

//Exclude the source file from upload because only 
//resized versions of the photo will be sent.
iu.addParam("UploadSourceFile", "false");

//Configure settings of the optimized image. Optimized image
//is resized to 1200x1200 with JPEG quality = 60 and EXIF 
//metadata is preserved.
iu.addParam("UploadThumbnail1FitMode", "Fit");
iu.addParam("UploadThumbnail1Width", "1200");
iu.addParam("UploadThumbnail1Height", "1200");
iu.addParam("UploadThumbnail1JpegQuality", "60");
iu.addParam("UploadThumbnail1CopyExif", "true");

//Configure thumbnail settings.
iu.addParam("UploadThumbnail2FitMode", "Fit");
iu.addParam("UploadThumbnail2Width", "200");
iu.addParam("UploadThumbnail2Height", "200");
iu.addParam("UploadThumbnail2JpegQuality", "60");

//Configure upload settings.
iu.addParam("FilesPerOnePackageCount", "1");
iu.addParam("AutoRecoverMaxTriesCount", "10");
iu.addParam("AutoRecoverTimeOut", "10000");

//Configure URL files are uploaded to.
iu.addParam("Action", "upload.lasso");

//Configure URL where to redirect after upload.
iu.addParam("RedirectUrl", "prescreen_results.lasso");

//Add event handlers.
iu.addEventListener("UploadFileCountChange", "ImageUploader_UploadFileCountChange");
iu.addEventListener("ViewChange", "ImageUploader_ViewChange");
iu.fullPageLoadListenerName = "fullPageLoad";

// Add additional data fields to POST
iu.addParam("AdditionalFormName", "Form1");

//Tell Image Uploader writer object to generate all necessary HTML code to embed 
//Image Uploader to the page.
iu.writeHtml();
//]]>