I just bought a perfectly new, including fresh out of the box of an Arduino Uno R3, but the screens for devices has it showing as a Atmega 16u2 DFU.
I do know that when plugging in the other one, an Arduino Duemilanove, that the system "twangs" and the system picks the FTDI one and it works properly.
I think I've got a device which needs to be returned to the store for replacement.
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via Egeo 16