Same problem. Water is not draining out to the back of the fridge into the evaporation tray. Ours has a little green piece of plastic in it which looks a bit like the thing you get in kids bubble mixture. It doesn't appear to serve any useful purpose. Replaced it with a cable tie - was the first thing I found with the right sort of size and rigidity. That seems to be working, as once poked into the hole, water started draining out into evaporation tray. 15 minutes in and seems to be working, no pooling of water in the channel at the back of the top drawer.
Of course now I'm worried that the evaporation tray will overflow, as this was a problem we had with the first one of these fridges - John Lewis replaced in the first couple of months.
Dave, June 2011