cash register samsung ser 6500?

till has frozen, when you put the power on the till will let u press around 12 buttons and then it freezes, the readout remains the same and dosn,t change no matter what u press, infact it stuck on the last transaction, have tried power on and off etc and cables connected all seems fine .............can anyone help..pleeeeeeease !!!!!!!!!! if u like u can ring my mobile on 07869 109807 many thanks