I just received a report from a customer in Japan. They tried *eight* times to check out, each time getting the error "Error: There was an error processing your payment: (10751 Invalid Data) There's an error with this transaction. Please enter a valid state in the billing address."
I can see no problem with their address, and the country was indeed selected as Japan.
From the Paypal virtual terminal guide, this error code should only occur for US and canada addresses. Can you please investigate?