I think I found a failure in this hack.
Line:
$ubbt_language = ${$config['cookieprefix']."w3t_language"};
seems to be wrong cause w3t_language is only the tables name if you did not change the preffix.
I am using cf as prefix therefore my table is called: cf_languages.
Check out
http://www.clanforums.com/mycookies.php for the (I think wrong) output. Can you please check if I am right and then please correct it?