I have seen this effect with neon and fluorescent lamps...the reason is that such lamps will show a visible glow with microamps of current. How can such a current flow with the switch off? The wiring (especially if it's the usual twin cable) capacitance will be enough if there's a reasonable distance from light fitting to switch. Two ways to get over the problem are don't use a looped in switch wiring; ie. have the supply come to the switch before it gets to the light fitting, or simply put a high value resistor across the fitting; something like 470K 1W.
Why the pulsed effect with a compact fluoro?
Again, the slight current flowing will slwoly charge up the electrolytic filter capacitor in the CFL. At a certain voltage the lamp will attempt to start (hence the short glow). But in doing so it draws lots of current discharging the filter cap again...voltage drops and lamp can't fire. Now that the lamp isn't drawing current again the procedure repeats itself and functions as a crude relaxation oscillator.
