Why energy saving bulb flashes when the switch is off?
For this to happen there must be some voltage to the light socket. It may not be noticeable with a standard incandescent bulb because it apparently is not the full voltage and current. If you are comfortable in what you are doing, you could measure the voltage across the two wires and ground to see what you get. Incorrect wiring could be the problem, such as an improper shared neutral leg, or the neutral being switch instead of the hot leg. This can be found using a voltmeter and referencing to a known ground. If your not sure, leave it to an electrician. Wiring is not a hobby, and can be lethal!