I've had problems with fan. The fan is used to blow / circulate cold air from the freezer compartment up to the fridge section. If any of the duct ways are frozen up , ( or the fan itself can stop working because of ice build up ) the fridge section warms up. As mentioned elswhere, try switching the whole thing off for 24 hours to defrost. Then start up again. If the fan dosn't work as it should, these are fairly cheap around £25 for part only & easy to replace.
Alan, August 2010