Somewhere in the back of the freezer you should find a drain hole. It is probably blocked. Once you locate it, push a soft flexible wiring cable down it. If you can't locate it inside the freezer go to the back of fridge. On top of the compressor motor will be a drip tray. Above it you will find the exit for the drain. Push the cable up from the bottom until it reaches the freezer. Once water comes down into the drip tray you will know that the blockage is clear.
Lincoln Appliance NZ, November 2008