The most likely culprit is your defrost heater, it is located in the freezer behind the panel. You will need to remove two hex screws one on the bottom left one about a foot up on the right, and remove the two philips head screws just under the ice maker. You will find the heater at the bottom of the unit held in place by two philips screws. You can find the part at most local appliance warehouses or I get mine from appliancepartspros.com, it is part number WR51X442… Hope this helps…
http://www.appliancepartspros.com/part_details.aspx?part_id=3687370&pn_=WR51X442
D. Hickman
January 2007