Hi. Yes, you got it. There is no one signed onto your machine. You simply sign an operator on, then it will work. Your book should tell you how, but the standard way is to press one of the clerk buttons at the top of the key board (A,B,D,E). If this doesn't work, then someone has setup special passcodes, and you are going to have to read the clerk program to see how it has been changed.
Feel free to get back to me if you can't sort it.
Mark, July 2008