When you add products to your cart then click the "Go to Checkout" button you get a 404.

This is the URL for my store:
http://www.doctorworkout.com/store/

The URL on the button is:
[url]http://www.doctorworkout.comhttp://www.doctorworkout.com/store/

These are my settings in both config files:
define('HTTP_SERVER', 'http://www.doctorworkout.com');
define('HTTPS_SERVER', 'https://www.doctorworkout.com');
define('ENABLE_SSL', 'false');

Any help would be much appreciated.

Thanks!