download prompt not woking on macintosh

Hi all I tried to build a script that displays the 'save-file dialog', because the files that should be downloaded are huge 32bit jpeg for printing. the problem is that it works in IE on PC, Netscape on PC and MAC, but not in IE on a MAC. the files are jpeg, IE on Mac either tried to open the files ( which does not work, because they are CYMK), or displayes the filename 'download.php' in the save dialog .... PLEASE HELP!!!! our designers can't be the only persons to use Mac on the world... i tried everycombination of the following headers, but without success... thanks sebastian code : /* header("Content-Type: application/octet-stream"); header("Content-Disposition: inline; filename=\"".basename($download)."\""); set_time_limit(0); readfile($download) or die ("File nicht gefunden oder sonstiger Fehler aufgetreten."); */ header("Content-Type: application/download\n"); header("Content-Disposition: inline; filename=\"$download\""); set_time_limit(0); readfile($download); /* header("Content-Type: application/download\n"); header("Content-Disposition: attachment; filename=\"$download\""); $fn=fopen("$download" , "r"); fpassthru($fn); */ /* header("Content-Type: doesn/matter\r\n"); header("Content-Disposition: filename=$download\r\n\r\n"); header("Content-Transfer-Encoding: binary\r\n"); readfile($download) or die ("File nicht gefunden oder sonstiger Fehler aufgetreten."); */ /* header("Content-Type: doesn/matter\r\n"); header("Content-Disposition: filename=$download"); header("Content-Transfer-Encoding: binary\r\n"); header("Content-Length: ".filesize($download)); readfile($download); */