I have just one light being controlled by X10. Often I will wake up in the middle of the night or come home from work and it's on. At first it scred the crap out fo me till I realized it was from X10. Any ideas why this could happen? Do I have a bad X10 unit? I have no timers of anything set for it either. Thanks.

Try a different house code... otherwise you might have some noise on the line. I'm sure others can help further.

The first thing I'd try is a new housecode like Daniel says. It is possible that someone else in the neighborhood is using that code and your home is picking it up. There are blocking filters available to assist in this but you may be able to solve the problem without one. If the unit is a in-wall switch, the code can be changed by removing the rocker part of the switch.

Also, there is software avaliable that can monitor X-10 signals. This can tell you if there is a X-10 signal causing the switch to operate or if is some noise or other source. Activehome and Commander-X have this monitor I believe. You would need a CM11A computer interface to operate this software.

Chris Couture

Also check for a loose connection or a bulb that isn't tight in the socket. If there's any intermittant connection in the system it can turn the light on or off at random.