Originally Posted by 
donf
				 
			Turn off the breaker, then disconnect the white and black wires.
Using a multi-meter, connect the black probe to the white lead and the red probe to the black lead.  Turn on the breaker and verify the voltage level.  Once you know that the circuit supply to the switch is correct than you can turn to the wiring of the switch.  You can also turn off the breaker and reconnect the white (Neutral) conductor to the White on the light fixture and the black to the switch.
Either you have miswired the pull switch or the switch itself is bad.  You can then test the input to the switch.  With the switch open, you should see 120 +/- on the input side of the switch.  If it is there, move the red probe to the output side of the switch and verify that the switch iws putting out the necessary voltage.
Can you send us a picture of the lighting fixture as well as the wiring work you did, please?