I have 4 registers with verifone mx830's and we've had nothing but problems since we got them, Sometimes and it seems to be completely random, the amount on the pin pad screen will be differetn than the amount on the register screen, other times, when the customer swipes their card and chooses credit, it asks for their pin number. Other times, when the customer swipes their card and uses the touch screen to chose what option they want it says "tansaction cancelled by customer " or "transaction cancelled by cashier". Other times, the unit will just freeze. Other times when the customer swipes their card, it will say "INV SHR GRP".