Hi everyone!
I was very interested in arduino so I bought a One (rev 2).
Since I couldn't upload any sketches, I've gone thru dozens of posts and tried the loopback test.. which failed 
At that point, I checked the revision of my ATMEGA8U2 firmware, and it was 0000
I then put the chip in DFU mode and flashed it with the latest (?) 0001 firmware. The operation was successful, and windows recognized the new device. After flashing the TX led was left on, so I know the led does work
Alas, the loopback still does not, and i fear my ONE is DOA
Before giving up, has anyone a suggestion of what else to try?
Many thanks to everyone!
Aldo, Italy