Freewilly: Do you have a phase coupler?
If not this may be the number one thing you
can do to improve reliability. FYI: I
wrote a tutorial on phase couplers. You
can read it at
http://www.x10.webhop.org/Phase_Coupling.htm Also, I highly recommend that you not plug
your CM15a (or any X10 device) into or near
a surge suppressor. Many surge suppressors
have noise filters which will absorb the
X10 powerline signal. Optimally you want
everything that will generate or absorb
powerline noise plugged into an X10
compatible noise filter which will block
both the noise and X10 signals (obviously
you don’t want to plug any of your X10
devices into one of these filters). I also
have a tutorial on powerline noise at
http://www.x10.webhop.org/Powerline_Noise_an d_Noise_Filters.htm
I hope this helps.