Paypal error on only one store-Your payment can't be completed.

Our new network of stores is working pretty well, but I have this one store that's having issues.

After you click confirm payment and it takes you Paypal screen, you login and then review information. But then when you click pay it simply says "Your payment can't be completed. Please return to the participating website and try again."

The store owner has a couple of different paypal accounts, all of them in very good standing, verified, etc. None of them work, but if I enter one of my own paypal accounts, or one of my partner's they work just fine.

Totally baffled. Anyone have any experience with this? Thanks!