Bug in Pay per View: "There was a problem finalizing your purchase with PayPal. Please try agai

When I buy one of my posts I'm redirected to Paypal and confirm the payment and so on. Everything fine so far. But then I'm redirected to my post, but I can't access it. Followed by two error messages:

10485 - Payment not authorized - Payment has not been authorized by the user.

10415 - Transaction refused because of an invalid argument. See additional error messages for details. - A successful transaction has already been completed for this token.

What to do, to make it work correctly?