The original post was sent in 2009. I want to reply for those of you that might read the posts in order to fix a similar problem. As in the original post, if you hear a popping sound this should be a clear warning that sparks are being generated from the broken light switch. Stop using it immediately unless you want to burn your house down
Make sure you have a fire extinguisher before doing the next step. If the breaker did not trip you should turn on the light and switch each breaker off and on till you find the breaker that turns the light off. That will let you know that the power is gone.
Now that you made sure that somebody isn't going to turn on the faulty switch go to a hardware store and buy a new switch. If you aren't sure what switch you need, take the switch's cover off and look at the switch and it's wire setup. Buy a switch that lets you screw the wires. I just changed some that allow you to quickly and easily insert the wire. Those are bad
because plug and switch movements tends to loosen the wires over the years.
As far as changing the switch, you should unscrew the screws that hold the switch to the wall receptacle. Then pull the switch slowly from the receptacle so that you can clearly see all wires attached to the switch. Whichever wires that you remove from the old switch should be bent to a position that will not let it/them touch any other wires and that will allow you to remember where it/they go(es) on the new switch. Screw the wires firmly on the new switch and leave it in a position that will allow you to test it. Test it by turning on the breaker and turning the new switch to the "on" position. If it works, turn off the switch and the breaker. Now reinsert the new switch into the wall receptacle--making sure the wires aren't crimped. Reinsert all the screws to make sure the switch is safe and tight. Then turn on the breaker and test the switch again. You just saved money and prevented a house fire.