Error on checkout

I just upgraded marketpress lite to marketpress premium. When I click on checkout button it returns error.

Firefox:

500 error

or

Firefox has detected that the server is redirecting the request for this address in a way that will never complete.

Chrome:

The webpage at http://domain.com/new/store/shoping-cart/shipping/ has resulted in too many redirects…

wp installed at “new” directory.

Single WP, not MU

Shipping Method: No shipping

Please Help