Go to a hardware store and buy an outlet tester just to make sure something isn't wrong with the wiring in your outlet. One time I plugged a computer in at a new apartment that my family had moved into. The outlet had been wired backwards or something and the power supply actually managed to catch fire. Afterwards we had checked it with the tester and that was how we found out.
Most likely it was a fault in your emac's power supply that caused it but you should make sure something didn't happen to your wall outlet prior to that or in the process.