Closed Issue: AjaxFileUpload control not working on IE9, Win 7 [27177]

I'm developing a site on .Net 4 on Windows 7 32-bit in VS2010. I've updated to the May 2012 version of the toolkit and tried using the ImageUpload of the HtmlEditorExtender, but whenever I try upload an image, it just puts a red (error) next to the image name. I've tried giving Everyone full access to the folder where the image should be saved, but I cannot even see that it is getting to that point. I've also tried using just the AjaxFileUpload control to test it, but it does exactly the same. Any ideas?
Comments: Please upgrade to the latest version of AJAX Control Toolkit v15.1. If the problem remains, feel free to post a new issue.