Hi Peter,
I'm having exactly the same problem as you.
Since it works on mains electricity I can't see it being a problem with the refrigeration gas ( ammonia). I have been told ( and seen on other sites) that if you take out the fridge and turn it over and over, leaving a few hours in between, it will free any blockage or air in the system. I am trying that now, so fingers crossed.
John Gray, July 2008