IE8 "Invalid File Type" Error

Hi,

I was doing some functionality testing of my store and found a problem which only shows in Internet Explorer8 (maybe earlier too).

I use a file upload function in the products and its giving an "Invalid File Type" error and refusing to upload the file. It works fine on IE9, Firefox & Chrome browsers.

Any ideas on why I'd be having this problem only on IE8 ??

Thanks..
Brian