Not sure if this will solve your problem, but try tossing in a
Content-Length header so the browser knows how long of a file to look for.
This helped - I can see the correct file length now in the download window. But now the problem is a little different. I can download .zip files with any browser, but .sit files do not decompress (Safari, IE6, anything). The whole file is downloaded correctly, but gives a Stuffit "damaged archive" error. Any thoughts? Here is my code now:
header('Content-Type: '.$file_row['content_type']);
header('Content-Disposition: filename="'.$file_row["filename"].'"');
$size = filesize('../../store/files/'.$file_row['filename']);
header('Content-Length: '.$size);
header('Content-Transfer-Encoding: base64');
readfile('../../store/files/'.$file_row['filename']);
Assume that filename = 'myarchive.sit' and content_type is 'application/sit'