Blizard, the serial monitor that comes as part of the Arduino tool set has some ‘guilty knowledge’ of the Arduino loader and trys to auto detect the speed of the serial link. The preprogrammed chip might not allow the serial monitor to get the speed set correctly. Try downloading ‘coolterm’ and using that; Setting the communications link to 9600 baud, 8 bits, no parity, one stop bit. If you google coolterm, you’ll find several sites from which to download it. There are versions available for Windows and Mac.