I've recently installed the Amasty One Step Checkout with "PayPal Website Payments Hosted Pro solution" as the payment method. The site uses the RWD theme.
The problem is when a user makes a purchase it goes through fine the first time, if they then try and make another purchase the checkout redirects to the paypal payment page with the message "Error Processing Payment".
The strange thing is if I clear the browser cookie labelled "frontend" it then clears the issue and a user can checkout fine again.
Any help would be much appreciated after days of talking with support and getting nowhere.
Thanks in advance everyone,
TythebarnDev