Arduino Uno R3 Power LED not flashing

First experience with Arduinos. Bought a new board plugged it in by USB, no LED power light… Played with it for 40 min (unplugging/replugging - refreshing system information/USB to see whats recognized). Finally there was a light and the USB modem- not configuration popped up. Opened the Arduino software and ran a example file which it operated perfectly. Then I unplugged everything put it away.

Today the USB modem-not configuration is still under system preferences, plugged in the Arduino and the Power LED light AGAIN doesn't light up…. whats the problem? Is it a faulty board? Or am I missing something?

I'm using an Mac OS X 10.7.5.

It was a faulty USB cable that came with the kit. Found one that works great!