Since this is a 14 year old appliance, I started with the least expensive, most common repairs with my particular model, exhibiting the same symptoms people described. I replaced the Defrost Heater and Bracket Assembly, the Defrost Limiter Thermostat and the 4 Temperature Sensors throughout the unit. Upon removing and inspecting the existing defrost heater, it was clearly damaged and worn, practically falling apart as I was examining it. The defrost limiter thermostat was discolored and also appeared to be worn and possibly damaged. The temperature sensors didn't look too bad, but the price was low enough to justify the repair as a measure of preventative maintenance. The unit started cooling immediately, but stopped at around 56F in the freezer, and got very hot to the touch in the center of the door frame, between the 2 doors. I called the number to talk to a technician, described the new problem and was advised that the rear cover should be removed and the condenser assembly thoroughly cleaned. It was pretty nasty in there and very hot. They offer a brush designed specifically for cleaning the condenser assembly, but I had one already and gave it a thorough cleaning. The unit cooled down immediately and in just a few hours was below freezing. The next morning, it was down to 0F and everything was back to normal.