If it's a frost free fridge then you'll probably find that the escape hole for water is blocked, this causes the water run off to build up as ice blocking the air flow which lowers the temperate of your fridge from your freezer which causes your fridge to warm up.
Bottom line, don't buy a frost free fridge freezer, you end up having to defrost it anyway.
If you take the back off and either use a wall paper stripper or a hot hairdryer you can melt the block of ice you probably have hidden away
I M Jolly
January 2011