Hi

I have a downstairs hall light that is controlled via 3 way switching, comprising of...1 triple gang near front door, 1 double gang upstairs and 1 intermediate switch by kitchen door operating the circuit with the multi gang switches other gangs operating other lights. Never noticed a problem all the while the fitting used 5 x G9 30watt Halogen lamps, but we decided to 'save the planet' and obtain LED replacements rated at 4 watts each. These offer great illumination, but....
When the fitting was turned off the LEDs could be seen to be glowing very slightly!   Took fitting down and checked everything visually and no signs of any issues, then I took a multimeter and checked Sw L to N with switches all Off. 61votls AC recorded hence the glowing LEDs.  Move each switch to its opposite position and the voltage is lost.  
So is it a defective switch or a cable defect?  I guess the easiest way to prove its a switch defect of not opening its contacts correctly, is to replace them all and see what happens? Unless there is a simpler way to test each switch?
Can you guys think of a faster and easier way of checking the circuit?

So LEDs now acting as fault finders too!  

Hi
Of course... Never thought about induced current/voltage in domestic wiring causing a problem!  
Will try a snubber ASAP. Just a pain in the whatsit to undo the light fitting to access SwL and N.  
Thanks for the heads up re snubbers.

I recently fixed same problem by fitting a ..

0.47uF Class X2 275VAC capacitor

across one of a set of downlights that was giving me this problem.