If you say so.

Not a way to talk to people looking for help and without having your php knowledge anyway.

But, anyhow, I fixed it by modifying your hack!
In the module:
I changed this:
PHP Code:
$db->query_write("UPDATE thread SET description = '" . $db->escape_string(htmlspecialchars_uni($edit['description'])) . "' WHERE threadid = '" . $db->escape_string($threadinfo['threadid']) . "'");
for
PHP Code:
$db->query_write("UPDATE " . TABLE_PREFIX . "thread SET description = '" . $db->escape_string(htmlspecialchars_uni($edit['description'])) . "' WHERE threadid = '" . $db->escape_string($threadinfo['threadid']) . "'");
Now it works...