The fan inside is iced up usually - I have a SAMSUNG RS21DCNS which is about 6 years old now. They should be unplugged for 24 hours at least once a year or the clicking sound will happen. Unfortunately mine is now doing it more often so I think that there is a thermostat problem as well.
DmC
February 2011
Automatic Answer
While you wait for answers, we may have found some information which could help you.