I talked about this here: http://www.ubercart.org/issue/1828/when_declined_entire_credit_card_numb...

It happens when an order is declined, and the user abandons the cart; or if something happens that causes the browser to crash and keeps the order "in checkout".. that will cause the full card number to not be processed along with Cron. (Might be an easy fix to include numbers from all orders).