Denise
I am afraid this is not an answer ... more of an agreement and continuation. I have observed the same on my fridge. The ice starts about 2 inches above the drip collection gulleys and within a day has travelled to the gulley and before long causes water drips to bypass the gulley and end up at the base of the fridge...
I have noticed that this only happens on the LH side and always in the same place. Makes me think that the LH side is colder (closer to the "source" of the coolant) and perhaps has a rougher patch on the back that initiates ice formation.
In my case, I wonder whether I could somehow smooth the rear surface of the fridge and stop the initial ice formation ...
John, November 2004