Thanks for your remarks.

I neither hold Amex nor Diners. The booking classes for discounted Business Class I am looking for are wide open on all flights. Problem occurs after schedule search on the final booking page.

According to EK's FAQ's it's my guess that some popup should come up after entering the cc details on the payment page for MC SC verification but this simply does not happen.

Never had this problem in the past (with VISA and prior to implementation of verification code).