file download/open and ie bug

I'm using version 6 of IE and Netscape I'm allowing the user to open/dowload a file from a secure locaiton on our server. Under Netscape it works great! Under IE, it doesn't work at all. IE complains about not being able to read from the server. Anyone know of any workarounds? here's the command I send: header("Content-type: {$mimetype[PDF]} \n"); header("Content-transfer-encoding: binary\n"); header("Content-length: " . filesize($fname) . "\n"); readfile($fname);