download header issue

I have some code for a download script: <? $filename = "source"; $ext = "tar.gz"; $mime_type = "application/x-tar-gz"; $filepath = "/path/to/src"; $fullfile = $filepath . "/" . $filename . "." . $ext; header("Content-Type: " . $mime_type); header("Content-Disposition: attachment; filename=" . $filename . "." . $ext); header("Content-Description: " . $filename); header("Pragma: no-cache"); header("Expires: 0"); readfile($fullfile); exit(); ?> It works fine in both versions of Netscape I have tried, 4.76 and 6.1. But IE wants to rename the file by adding a [0] or a [1] into the filename so I end up with "source[0].tar.gz" or source[1].tar.gz as a suggested filename. If you keep trying the download the numbers go on up to [2] or [3] or [4] like it's incrementing or something. This even occurs if you cancel the download, so I'm pretty sure nothing is being cached. What do I need to change in my script to keep IE from doing this renaming thing? Thanks, Greg