When you open the door warm air rushes in and hits the back wall of the fridge,condenses and forms droplets(like your windows)most fridges have a V shape in the plastic back wall with a small hole at the bottom,the water runs down the V and out of the hole and evaporates out the back of the fridge,the hole can get blocked with food particles and needs cleared out,it may have a small plastic tab sticking out of it that you wiggle around to clear it but most just have a hole,see that it's clear.Try that first to see if it solves the problem,clear the ice off the wall as it may have frozen over the hole.Also if you can pull the fridge out Hoover all the fluff and dust off the wire grill on the back(it will be there).
Rich, May 2008