fpassthru failure with mozilla

I'm using fpassthru so users must log in to have access to certain files. The users are accessing the fpassthru script with an https connection. The code works fine with IE but sends inline ascii text with mozilla/firefox. The code looks like this: $filepath = "bla/bla/files/"; $filename = "file.zip"; $fullpath = "$filepath/$filename"; header( ' Pragma: '); header( ' Content-Type: application/force-download' ); header( ' Content-Type: application/octet-stream ' ); header( ' Content-length:'.(string)(filesize($fullpath))); header( ' Cache-Control: private' ); header( " Content-Disposition: attachment; filename='$filename'"); $fh = fopen("$filepath/$filename", "rb"); fpassthru($fh); Any ideas? Everything I've read says with the content type set to application, and the disposition set to attachment I should be set, but it doesnt seem to be the case.