OK, I found the problem.

ultimatebb.php has:
Code
	$in = rawurlencode(find_environmental("QUERY_STRING"));
But do you remember the ";" bug? So it thought $in->{ubb} is 'get_topic;f' (until the next =), and it's not in the list of commands.

Fix: Replace that line with:
Code
	$in = rawurlencode(ereg_replace(";", "", find_environmental("QUERY_STRING")))