RISOLTO:

Modificare il file mkportal/modules/download/index.php
trovare il codice:

Codice PHP:
@header"Content-Type: application/octet-stream\nContent-Disposition: inline; filename=\"".$file."\"\nContent-Length: ".(string)(filesize$real_file ) ) );
$fh fopen$real_file'rb' );
while(!
feof($fh)) {
$buffer fread($fh4096);
print 
$buffer;
}
@
fclose$fh );
exit(); 
e sostituire con:

Codice PHP:
@session_write_close();
   @
ob_end_clean();
   if (!
is_file($real_file) || connection_status()!=0) {
   die(
"Download failed");
}   
set_time_limit(0);
   
$name=basename($file);
   if (
strstr($_SERVER['HTTP_USER_AGENT'], "MSIE")) {
   
$name preg_replace('/\./''%2e'$namesubstr_count($name'.') - 1);
}

   
header("Cache-Control: ");
   
header("Pragma: ");
   
header("Content-Type: application/octet-stream");
   
header("Content-Length: " .(string)(filesize($real_file)) );
   
header('Content-Disposition: attachment; filename="'.$name.'"');
   
header("Content-Transfer-Encoding: binary\n");
   if(
$h fopen($real_file'rb')){
   while( (!
feof($h)) && (connection_status()==0) ){
   print(
fread($h1024*8));
   
flush();
   }
   
fclose($h);
   }
   
exit(); 
da http://www.mkportal.it/support/showthread.php?t=9069