Programmable switches or dimmers can cause this, due to a very small leakage voltage triggering a capacitor somewhere in the bulb. Any 'leakage', [say a track on switch insulation] can cause this too- it can be so small as to be unnoticed when using filament bulbs. Since it is a 'load' it will not trigger an RCD or GFCI. Some CFLs also glow dimly for a short while when turned off. IMHO, not worth worrying about.
Last edited by Alan Belson; 04/02/10 06:54 AM. Reason: syntax