Hmm... so having the laptop power supply and the cm15a plugged into the same circuit causes issues. WTF?? Since you have to have a computer to run the CMA15a and get security emails you would think that whomever designed the CMA15a would have figured out that since the computer and cm15a have to be plugged together via a USB, that it would be highly likely (like what, 100% likely???) that they would have the same power supply?? That is so stupid that I it boggles my mind.
I think you are reading to much into it.
SOME switching power supplies put electrical noise on the powerline (they come in all forms, but cell phone chargers, notebook "power blocks", computer power supplies, CFL bulbs, etc. are good examples of switching supplies that
may be noise makers).
If this noise contains certain frequencies it can corrupt the X10 powerline signals. X10 corporation has no control over this and they really have no way of fixing it, other than to offer filters which block the noise. Since the offending noise is of the same frequency as the X10 signal, these filters will also block X10 signals. So the filters can not be incorporated in to X10 devices, otherwise they would block the incoming or outgoing code.
The idea is: once you find a noise maker you plug it into a filter (like the X10 Pro XPPF,
http://www.x10pro.com/pro/catalog/platform.html#filters) and the filter will block the noise from getting on to the homes powerlines.
Another way of combating powerline noise, which has been previously mentioned, is to use a good (X10 signal) repeater coupler.