[NuclioN]

Yes, the db modifications are correct. Also i've no prefix for the tables.

In editpost.php there are 2 lines of this code:
attach = attach + $newattachments

The first one is for 'UPDATE " . TABLE_PREFIX . "thread SET..'

The second one is in here:

UPDATE " . TABLE_PREFIX . "post
SET title = '" . addslashes(htmlspecialchars_uni($edit['title'])) . "',
pagetext = '" . addslashes($edit['message']) . "',
allowsmilie = $edit[allowsmilie],
showsignature = $edit[signature],
iconid = $edit[iconid],
attach = attach + $newattachments
WHERE postid = $postid
");