IE not support UTF-8 MIME attachment filenames

Like bug reported in http://drupal.org/node/755578, attachments private downloads in Internet Explorer fails to show and save the correct filename when this filename uses UTF-8 characters. I solve this issue with similar code show in the previous report:

Changing line 195 and 196 in filefield.module:
$name = mime_header_encode($file->filename);
$type = mime_header_encode($file->filemime);

to:
if ( eregi("MSIE", getenv( "HTTP_USER_AGENT" )) || eregi("Internet Explorer", getenv("HTTP_USER_AGENT" ))) {
$name = mb_convert_encoding($file->filename,"ISO-8859-1","UTF-8") ;
$type = mb_convert_encoding($file->filemime,"ISO-8859-1","UTF-8") ;
}
else {
$name = mime_header_encode($file->filename);
$type = mime_header_encode($file->filemime);
}