Hmmm...interesting...just right-clicked on the actual UPLOAD button and a Silverlight tag comes up! This control is built with Silverlight but IE 9 has a problem with it? That's Micosoft BS for you!
I have also tried adding <meta http-equiv="X-UA-Compatible" content="IE=8"> but that doesn't help either - which I don't fully understand cause that usually provides a workaround for IE 9 issues and this control works in IE 8.