Flat rate and free shipping conflicting

Regarding the shipping costs, I have a flat rate set for entire order (even of more items) of 4€, and free shipping when order is more than 48€. A customer start to order items and if he doesn’t reach 48€ the shipping cost is 4€, and this is OK. When the customer reaches or goes over 48€ he is eligible for free shipping but on the checkout page now appears 2 radio buttons or select boxes to choose flat rate (4€) or free shipping.
After having reached the threshold of 48€ only the free shipping option should appear, with no select boxes or radio button.
Anyone has met this bug and solved it? Or anyone knows how to help me?
Thanks in advance.

http://wordpress.org/extend/plugins/woocommerce/