I have recently had the same experience. Literally 3 inches was all that worked. Since then I have have since tried 3 different CM19a (have a 4th on the way) and 2 different TM751s. I agree, very unreliable equipment.
Here is what I have done to come up with an x10 basic install that is (mostly working).
- move a separate PC out into the garage away from my other electronics that x10 said were likely the issue
- tried varying combinations of cm19a's and tm751's until I could get something that most worked.
- extended the cm19a antenna with extra wire (suggested by x10.com) - anyone know of any better mods for this?
- extended the cm19a with first 8ft usb extension an then 18 foot.
- extended a ds10a mag switch wire to within feet of the cm19a, but it still doesn't sense reliably.
- spent about 30 hours getting a basic install up that x10 assured me was 'plug and play' - I never bought that to begin with, but it's been a bit crazy.
Seems a bit like now that the CM15A's are gone new x10 installs are very hit and miss. Considering boxing it all up and sending it back, but now I'm a bit hooked. Never could walk away from a puzzle. I think that might be in x10.com's marketing plan?
But seriously, if they want this any furture repeat customers they are going to have to come up with a better option than the Cm19a. Even a cheap direct to PLC usb interace, that at least worked. Or better repeaters? Something!