I have the same problem.
I don't know when it has begun, but now, I can't download attachment with accentuated characters.

Mantis : 1.0.7
Charset in MySQL : Latin1
language : french
$s_charset = 'windows-1252'; in lang/french.txt to support copy/paste from Word (with file encoded en UTF-8)
custom_strings_inc.php encoded in UTF_8

I tried the fix from prima... but it doesn't work for me :-(

Someone can help ?

Thanks

I have the same problem,too. I fixed with in line 86 file file_download.php

Mantis : 1.1.0a3

if(preg_match( "/MSIE/", $_SERVER["HTTP_USER_AGENT"] )) {
header( 'Content-Disposition:' . $t_disposition . ' filename="' . urlencode($t_filename) . '"' );
} else {
header( 'Content-Disposition:' . $t_disposition . ' filename="' . $t_filename . '"' );
}

Did anyone got a chance to test James_Fu's fix?

James_Fu, why do you only urlencode the file name in case of MSIE? Should we do it for all browsers?

I test IE6 and FireFox. If I not fix it, only IE download filename is not correct.