Try unpluging the PC, not just turning it off. If that does not help, try truning off all the breakers except those needed to control the X-10. If it works, slowly turn them back on and test after each time. If you get to one that caused problems, flip off all except that one and the X-10 one. If the problem is still there, what is on that breaker that could be causing noise (if noise is even the problem)?

How big is the house? Have you thought about a amplifier or amplified coupler?

Do you only have the Activehome to control the X-10 or can you try a handheld remote or other X-10 transmitter? Sometimes the signal from the CM11a interfaces are weaker than other transmitters. This won't help you much but may tell you that the switch is to blame.

Have you tried to reverse the switches to see if the problem follows the switch or is the location the problem?

Chris Couture