I encountered similar problems trying to book the previous Caribbean sale fares. The system failed to complete the transaction at the verification stage, the on screen advice was to call a help line, which was in fact the Indian call centre. Their response was that the booking had not been made but they were unable to make the booking at the same price.
I subsequently booked on line the next day, this time without the verification process. My additional concern was that despite the failure at the first attempt, provisional authority for the charge had been taken. Although the charge was not made it remained in 'unposted items' on my bmi mastercard account for almost a week.
Makes the already challenging on-line booking process even more difficult..