Screen hangs after cash transaction or credit card...

Question

Restaurant POS after order is taken and sceen pay icon is pressed the till opens, but the screen hangs, the more items ordered the longer the screen hangs. If customer is using credit card then the hand time is really long. Dell optiplex 755, server 2005. One server as main register and client pos is secondary for window drive thru. The client station has no problems whatsovever only the primary.