I have a client with a similar issue. They are using MAS 200 version 4.4.5. They enter most orders using Sales Order Entry. In SO Entry, the credit card comes up on screen, pre-authorizes and runs correctly. But, on occasions when the customer was coming in to pick up the product and they weren't sure when the customer was coming, they wouldn't pre-auth the card in SO. Instead, they would wait until the customer came in and then go to SO Invoice Data Entry, enter the order and credit card. When doing this, the wrong customer's credit card would sometimes come in. They could tell the wrong customer was coming in when the validation code would come in blank. I worked with Sage on the problem to no avail. We ended up with a work around of entering all orders in SO Sales Order Entry and then invoicing from there. The problem also seemed to go away when the employee rebooted her workstation. It appeared that the prior customer's credit card info would get stuck in the system and rebooting would clear it out.