enable query strings problem

[eluser]dimis[/eluser]
I have an e-commerce site and we have a payment via card.
The bank url redirect at our dite with the url

(site url)/card/bad?ref=5

but I thing because of the

?

there is the error 404 Page Not Found .
I set up at config.php the

Code:

$config['enable_query_strings'] =TRUE;

but still there is the error 404 Page Not Found .
What is wrong?
Dimis