I've had my v4 kegerator for 4 months now, and have noticed the occasional drip of consensation coming from the copper pipe at the back of the unit. Apparently there is meant to be some insulation covering the area, and my fridge didn't come with it.
I emailed Kegking, and they have sent out a piece of kflex tubing to fix the problem. They say that a number of units were sent out without the tubing for some reason.
After tightly attaching this to the copper piping with cable ties, I can report that there are no more drips.
Check the back of your unit. Even if there is insulating pipe attached, it may not be in close enough contact with the copper piping, or there may not be a sufficient length to cover the copper pipe. I showed my lhbs owner on his kegerator, and his was dripping condensation with insulation attached. A small rust patch had started forming on the galvanised base.
Sorry for the long post, but I thought people ought to know. Kane from kegking was very helpful, by the way.