Here's an easy fix for LED lamp glow (and perhaps flicker) with X10 modules (AM466 appliance modules in particular). Recently I replaced several outdoor halogen floodlights with LED units and was surprised to see that they remained ON (faintly but definitely) even when switched off. I had assumed that the appliance modules, which click audibly when switched on or off and which have no dimming function, were simple relays . . . but it turns out that, like the dimmable lamp modules, they emit a small current. This doesn't make incandescent or halogen bulbs glow, but it does so with the efficient LED's.
X10 websites show many schemes for modifying the AM466 to defeat this; it relates to "local control" current, and it involves clipping resistor(s) and/or diodes. Unfortunately, there are many different makes and models of the unit with different circuit board layouts, and the online plans don't distinguish among them.
Fortunately, along the way, I saw mention of hooking a small load such as a night light in parallel with an LED lamp to draw away current and eliminate the glow. This would of course just replace one glow with another, albeit the night lights could be tucked away in the cabinet with my X10 modules. Then I saw mention of using a small AC adapter, e.g. a phone charger, typically 1W or less, as the load. One simply plugs a splitter/adapter into the X10 module and then plugs in the LED lamp and the dummy load in parallel.
I have a whole collection of AC power supplies in different sizes; I tried a couple of the 5V units, which are most plentiful, and mirabile dictu no more glow! I ordered several inexpensive USB phone chargers, and alas these didn't solve the problem; they replaced the steady glow with an intermittent glow, flickering about 1/sec. Perhaps these use solid state switching rather than good, old fashioned transformers . . . In any event, I've gone back to the older power supplies, and these work very nicely. It's a simple plug-and-play solution.
I wonder what principles are involved here, and what dummy load (resistive, inductive, etc.) would be ideal (lowest power, lowest cost)? Would a similar approach work for dimmer modules? I have some dimmer circuits with multiple lamps which will accept LED's as long as one halogen bulb (resistive load) remains. In a dimmer circuit with a single lamp, I wonder what load might be plugged into a socket adapter, in parallel with the lamp?
