I was talking to Greg today and I forgot what this message meant. Apparently you need to check the phone line to see if there is an issue. So try calling your cc computer number and see if the line works. You can also check the line with your hand held by dialing out and posting. Could be your modem also?
http://www.autocareforum.com/showthread.php?12436-Hamilton-CC-on-acw-4-saying-card-unreadable-Help