A pint is yours if you can solve this conundrum for me (a theoretical explanation you can convince me of will do; I have a practical workaround).
A few weeks ago I replaced some of the bulbs in my house with energy-saving ones. However, the ceiling light in my hall behaves in a very odd manner. Occasionally, after I switch it off at the wall, it flickers on very briefly (for about 1/10 second) about once every minute - even though the power is (allegedly) off. The flicker is fairly dim, so I only notice it at night. If I take the bulb out of the socket, the flicker stops. If I put it back, it starts again. This behaviour happily continues for hours - to the extent that I remove the bulb when it happens because it’s too distracting when trying to sleep.
Perhaps it’s some kind of residual charge in the bulb. But this doesn’t really seem to explain why it only flickers when the bulb is in the socket (even though the switch is off). It also doesn’t explain why it doesn’t happen in the rest of the house (they have the same brand of bulb). The only difference is that the hall has two switches - but they aren’t dimmer switches or anything special.