Force Download file to Mac i.e.

I really,really need someones help !! I am writing an app that must force download Jpeg files on both PC and Mac versions of i.e. The PC version works fine but the the Mac version either prompts but then doesn't have the correct filename, launches the download manager but with the wrong filename or displays the image. (depending on different headers I use). $fname=$filename.".jpg"; $fp = fopen($fname, "r"); header("Content-type:application/octet-stream"); header("Content-Disposition: attachment; filename=$fname"); fpassthru($fp); How can I force the name on the mac !! I can get this to work for PDF files etc but not images, why? Please help. Leigh