Order denial when placing order

We are experiencing customers that fill their cart and when asked to place the order the screen turns to computer jargon. It comes through in the Admin as an incomplete order and does not contain the shipping method or the credit card information even though that information was entered.

Further attempts by the customers to place the order turn out the same way.

This does not happen to all customers and it seems to be random.

Any help with this will be appreciated.