Can no longer login!

After edeting Checkout.php, installing own plugin and translating after reading your translating manual, i can no longer LOG IN to my wordpress on my domain http://www.hurtigdeal.no/wp-admin .

I can still enter http://www.hurtigdeal.no as a guest, but when adding to cart, the whole shoppingcart dissapares.

Very strange.

I have tried to restore checkout.php.

Can anyone help?