PayPal Standard issue

Dear Support,

We need your kindly help. We are using free version of your plugin with PayPal Standard, and love your plugin – but PayPal is not working except the buyer has money on PP accout. I mean, if buyer would like to pay with credit/debit card, after log in to their PP account, they got error message:

At this time, we are unable to process your request. Please return to … and try another option.

Have you ever seen that kind of problem?

Thanks in advance!

The page I need help with: [log in to see the link]