When using PHP-eSeller, if you are using the download login pages within https rather that http you may have to do a modification to the login_downloads_file.php
The modification is necessary to fix a bug in Internet Explorer for https SSL as explained on http://abeautifulsite.net/notebook/27 and http://support.microsoft.com/kb/316431
The change is to remove header(“Pragma: no-cache”); and replace with header(‘Pragma: private’);