need some help to get Arduino NG (atmega168) up

Hi I am new to Arduino and to the forum. I have a Arduino NG board with Atmega 168. Green Power LED comes up when connected USB to Mac. Selected Board and Port. Trying to upload any sketch (e.g. blink) results in short blink of RX LED and error message avrdude: stk500_recv(): programmer is not responding on Arduino application Any idea what I do wrong? Regds Rico