title: 500 internal server error on magento checkout
body: <p>Everytime I try to checkout as a user in the magento site I've been working on I keep getting an error. It happens when clicking on the checkout button or by going to /checkout/onepage. Sometimes it will be an internal server error and other times it will show a couple lines of the accordion menu. This only happens when I am logged in as a customer. Checking out as a guest has no issues and registering at the time of checkout also has no issues. You can view the site at <a href="http://www.wadjetworldwide.com" rel="nofollow">wadjetworldwide.com</a>. </p>