it concerns me when switching on or off one appliance causes a reaction in another.
e.g. when i unplug my amplifier, my screen turns black for a second.
it used to be when i turn off my desk lamp, my keyboard would light up, even though the PC is off (and the lamp wasn't connected to the PC in any way).
i suppose it must be like a brief disturbance in the AC wires that causes power supplies to misbehave. or perhaps some kind of ground-loop effect.
maybe someone who's into electronics could guess at what might be going on here.