Comes back to this question, X10 brand switches have a power sense circuit that sees power dips as a remote on command. This was put in so you can turn on light module just by switching an off lamp on and off a couple of times. I would say your problem is probably related. Only fix on this is to get your power stable or switch to a brand of X10 that does not have this problem.

Bill
www.homeautomationnet.com

the key thing here too is who manufactures the switch..its possible to have noise coming from cordless phones. microwaves.. anything with a hermetic compressor can send noise down the lines as well..
Id try a switch that x-10 protocol but also PLC (power line carrier) try some of the switches by on-q or UPB. If you are using the cheap switches sold by smarthome or something in comparison then id look elsewhere for swiches..a good QUALITY switch will cost more than 40 bux and is well worth the headache.
As far as a phase coupler i have have homes now that are 7k square feet without the first phase coupler.
True they can be benificial but if you dont have crap clogging up the lines then your signals will no be delayed nor will they dissipate

Any professional installer I know would never dream of doing a home with X10 without a good phase coupler. Get yourself a signal analyzer and look at how a signal travels in the home and you will understand why. Interestingly even UPB technology requires a coupler; you just can’t get around the physics of the problem of not having one.

Bill
wwww.homeautomationnet.com

Although I don;t know nearly as much as the longstanding members here, I've used the x-10 system personally in several different locations for over 20 years. Recently I began having lights coming on unexpectedly and repeatedly, one unit code in particular, but others also. It was shortly after I plugged in a new computer....I use a wireless network, with bluetooth, and also added a new printer. But this didn;t seem to be the cause. I've never used a noise filter, so I ordered several, but they didn;t yet arrive. It seemed very unlikely to be from neighbors as I live in a rural area of homes each on several acres and the same unit would repeatedly turn on in the middle of the night....unlikely a neighbor was sending that repeat signal. When I unplugged a RadioShack mini timer, (Yeah I know its cheap and junk) the faulty signals seem to have stopped. ? cheap equipment suddenly failed/short circuited. I'd consider that seems the likely culprit in my case....possibly in yours also.

One more item to consider -- if you are using an X-10 RR501 receiver with a wireless controller and the RR501 is getting old, it could be sending random commands. I experienced this problem recently with a 10+ year old RR501. Found the problem by porocess of elimination, added a number of filters, etc. with no improvement, disconnected the RR501 and the problem stopped, reconnected the RR501 and it came back. I replaced the RR501 with an all houssecode unit (V572) and have no further problems.