PayPal error after taking live - urgend help needed

Hi,
after publishing the website mit marketpress shop on:
http://www.maatka-re-kartenlegen.tv/shop-mr/

I get now Errors at the checkout with paypal:

There was a problem connecting to PayPal to setup your purchase. Please try again.
10401 - Transaction refused because of an invalid argument. See additional error messages for details. - Order total is invalid.
10426 - Transaction refused because of an invalid argument. See additional error messages for details. - Item total is invalid.
10413 - Transaction refused because of an invalid argument. See additional error messages for details. - The totals of the cart item amounts do not match order amounts.

I've also refreshed the API information at paypal directly. But the issue seems to be at another place. Also updated to the latest release.

Please let me know how to fix the issue.
Thanks a lot !
Greetings
Michael