Moderator Post (s) for this thread: >Here's a link:bydoug seibert on 03/19/2011
At least one of the two switches is miswired. He has probably swapped the common and one switch leg. Which is which? There is no way to know since we can't see the wires and there are no standard colors so we can't say "Switch the red and black wires on the switch at the kitchen door."
There are as many ways to get the proper connection as there are electricians. There is only one way the circuit will work properly but the actual connections and wire colors are almost infinite. There is no standard for the connections on the 3-way switches either, so that adds even more confusion. Some have the common on one side and the switched connections on the other. Some have all connections on one side. There is no way to know what the wiring on the switches is without seeing them or reading the instructions for them.
Just have the friend come back and figure out what he did wrong last time. It's easier than us trying to guess at what he did.