I just moved into a brand new house. My X10 stuff came along and just plugged in and worked. The only problem is with my dining room. Nothing works in there. Well, almost nothing. I have a chime that did work in that room.
I have a small lamp with an attached lamp module that I can carry around, and I've tested every outlet in the dining room, and other rooms. Only the dining room seems to have any problems.
I initially thought it might be a phase problem with that room, but I added a 4 prong dryer phase coupler. That had no affect other than to stop the chime from working. It was pretty difficult moving the dryer to install it, so I'm not planning on removing it.