Fixed in CVS several weeks ago.

hmmm. my hoster still has this bug, 
i just reported this as "note" for other users to have a work around.

<?php
function readfile_chunked($filename,$retbytes=true) {
   $chunksize = 1*(1024*1024); // how many bytes per chunk
   $buffer = '';
   $cnt =0;
   // $handle = fopen($filename, 'rb');
   $handle = fopen($filename, 'rb');
   if ($handle === false) {
       return false;
   }
   while (!feof($handle)) {
       $buffer = fread($handle, $chunksize);
       echo $buffer;
       if ($retbytes) {
           $cnt += strlen($buffer);
       }
   }
       $status = fclose($handle);
   if ($retbytes && $status) {
       return $cnt; // return num. bytes delivered like readfile() does.
   }
   return $status;

}
?> 

kind regards 
flobee