[eShop] Payment failed, but not really…

Hi.
We are using eshop in our wordpress site at the moment.
Although payments/orders are going through successfully (ie the money is going to paypal), the eshop back end classifies every order as failed. It then emails us stating it has failed…. normally at the same time paypal send confirmation that we have had a successful payment.
I have the shop setup using our primary paypal address.

Thanks in advance