Modules switch on every second

["geo" <george.stachnik@xxxxxx>]

I'm a newcomer to X10 (although I used to play around with Radio Shack
Plug-N-Power units many years ago, which I understand are the same
thing).  I recently Bought a kit consisting of the HR12A Palmpad, TM751
Transceiver and the LM465 lamp module.  Now for my problem.

I plugged a lamp into the TM751, and it worked fine.  But at the other
end of the same room, (next to our TV) I plugged another lamp into the
LM465, and it started blinking once every second or so.  I had an old
Radio Shack appliance module laying around - and did the same thing.
Both units respond to an "on" command.  But when you turn them off,
they revert to the blinking behavior.

I suspect the problem may be linked to our Dish Network satellite dish.
 The box on top of the TV is connected via a phone line to a box that's
plugged into an AC outlet.  At the other end of the room, a similar
box, also plugged into an AC outlet, is connected to the phone line.
I'm guessing that the Dish Network set-top box uses something like X10
signals to talk to the box that's connected to our phone line.

Is there some kind of filter I can use to keep the two separate?