Hyrules, I had similar problems with ghosts
turning on my lights at night. After many
trials and errors and many bucks in filters
I found it. Defective X10 light switches!
Unfortunately, the bargain switches sold
here are often the cause of the problem
itself. Try replacing some switches by the
SwitchLinc model sold at SmartHome. It seems
also that the more switches you have, the
more likely this ghost lighting phenomenon
is to show up. Ten X10 pro switches seems to
be the limit in my case. More than that and
lights start to turn on in the middle of the
night (I have 15 X10 switches around the
house, 10 of them are X10 pro).
In hope this will help you a bit.
Sylvain Bombardier