The uploader should work fine, and I just double-checked myself that it works in IE. Maybe try upgrading your IE, see if that helps? IE8 has been officially released, and I've read that MS is putting it in automatic Windows Updates to try and get most remaining IE6s updated since it's become a security risk.
Your account appears to have about 46MB available, so is the file you're uploading smaller than that? You should be able to click Browse, select a file to Open, then click Upload, after which you'd see a "Please wait while the file uploads" and "Initiating upload..." message, and you're done. You should be able to see stats for the latest-uploaded file for that product on the first screen of the product's settings.