I'd say the thermostat may be broken or set too warm, set the thermostat in the freezer (if it has 1 there) to its MAX. setting or if there is only 1 thermostat for the whole fridge, set that to MAX.
Sometimes frost free systems need defrosting just to clean them up a little, someone else on the net had a freezer that just 'stopped' he turned it off for around a day to defrost (it was frost free) and then plugged it in again, and it worked. Try both of my ideas and reply, I'd like to know if this helped!
Aren Harris, March 2010