Mac Arduino Uno Not Showing Up

Development Tools IDE 1.x
1

I am running Mac OS X 10.9 on a MacbookAir. I just received an Arduino Uno R3. I installed the Arduino IDE and then plugged in the Uno. The Uno is receiving power, but my Mac doesn't appear to recognize that it is connected. The getting started guide said that a dialog for Network Preferences should appear, but a window never appeared. The console shows no output when I plug and unplug the Uno. The System Information shows nothing attached to the USB port. I have tested the USB port, and it is fine. I have also tried plugging the Uno into a different USB port. I would greatly appreciate any insight.

EDIT: I have now also tried plugging the Uno into a Windows computer. It shows similar symptoms of powering the Uno but not recognizing anything plugged in.

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Is it a genuine "Made in Italy" Arduino UNO or a clone?

It sounds like the firmware on the 16u4 processor (used for USB-to-Serial conversion) is broken. Here is the page that describes how to refresh to firmware: http://arduino.cc/en/Hacking/DFUProgramming8U2