Try this:
in addpost.php, line 418:
$Body = str_replace("&","&",$Body);
$Subject = str_replace("&","&",$Subject);
[:green]$Subject = str_replace(""",""",$Subject);
$Body = str_replace(""",""",$Body);
$Body = str_replace("<","<",$Body);
$Body = str_replace(">",">",$Body);
Add the green line.
I only did a preliminary test, it works. However, I don't know if the $Subject should perform those str_replace() functions as $Body does.
Regards,
Wenshih