There is a very easy trick to try if your garberator stops working.  On most machines if you feel the bottom there is a little button.  Press the button and try using again.  The button is a reset switch and sometimes it will turn its self off to prevent overheating.  If that is not the issue make sure the plug is inserted all the way into the socket.  Next i would recommend checking the electrical panel and make sure the circuit breaker has not tripped.

If either of those things are O.K. then it might be time to call a licenced plumber.