Parallax PING))) Ultrasonic Sensor #28015

sounds like loose or bad conection, either the pin sockets are bent loose on the ping side of the blug or the wire guage is to small on the stamp breadboard side but first double check the code section by comparing it to the example code offered by parallax, then if its not the code. 

option 1 using a larger guage "copper" wire to assure good bread board connection  and solder the wires directly to the pins on the ping.

option 2 buy a new "parallax" 3pin servo cable.<-Errrr I hate saying that

if none of these fix it and it did work before, it probably either has a bad componant caused by reverse polerization ,over voltage or has a bad solder on the board <-check that.

 rebember

Vss is ground

Vdd is regulated 5V

Vin is the 9V supply battery

and that leave you at option 3, fix it or buy a new one..

how did it break?

If you can describe the casualty to me I can walk you through the repair.. I think that is the part about being a Engineer I like, "Nothing goes to the junk box in the sky, I get to keep and reuse it all!" moy-AH-AH-AH! <-mad scientist jargon

If it's a componant it can be replaced if its a pin or circuit trace a few wholes drilled and a jumper wire soldered in place.

 if you just like trhowing money away be my guest or mail it to somebody who will fix it make a friend or be a soldier, buck up and fix it! 

 I think the pir and ping are both great for guys just starting out but personaly go with using componants and etching my own sensors now days. photo diode and IR led and a few timing circuits is all you really need and I think it's well documented here on LMR. Either way Good luck.