Here is the problem:
at this page: http://www.domain.com/onestepcheckout/ The customer fills out the fields on the onestep checkout page, select their country as "United States" from the drop down menu, which displays a new dropdown list called "County" which contains all of the states in the US.
The customer picks one of the states, chooses their shipping method, selects paypal as the payment method and then clicks "Place order now" button.
Instead of going to the paypal website to complete the payment, the customer is redirected back to http://www.domain.com/checkout/cart/
The checkout works correctly when using other countries which do not have a dropdown for "county" / state.
What can I do to fix this problem?