PayPal interface login problem for customers

My customers are getting this message repeatedly when attempting to make payment.

“We cannot process this transaction because there is a problem with the PayPal email address supplied by the seller. Please contact the seller to resolve the problem. If this payment is for an eBay listing, you can contact the seller via the “Ask Seller a Question” link on the listing page. When you have the correct email address, payment can be made at .”

Anyone experienced it or have any ideas? Cs Cart say they cant replicate it and it is with PayPal. PayPal say it is a cart issue. :frowning:

Any help or similar experiences would be appreciated. :smiley: