If you take a look at the other problems on this web site you will see it repeated. I can tell you a quick fix but as yet I do not have a full repair answer. What is causing the problem is a build up of ice in the freezer dept because the freezer is not auto defrosting. If you remove the goods in the freezer compartment you will see 6 screws holding a white sheet metal plate at the back , remove these screws. At the bottom you will see a plastic cover held on by 4 screws, remove this, you will also have to remove the 2 rear shelve brackets which house the wire grid shelf. The white sheet metal strip should now pull up and out. You will then notice the condensor is iced up, you must remove this ice with a hair dryer/ steam gun. At the bottom right of the freezer compartment you should feel a passage that leads to the fridge, ensure this is not blocked with ice. Re-build and test. Sounds a bit tricky but its easy once you have done it.
Mark Eastwood, October 2008