What's wrong with my Maytag frige freezer?

My side by side Maytag fridge/freezer is staying cold enough and making ice, but every once in a while the freezer side leaks about two cups of water on the floor in front, and there is leaked water on the bottom of the freezer inside that is forming a thick layer of ice. The metal coils inside the back of the freezer are slowly dripping water inside, thus the build up of ice on the bottom... What's wrong?