cyberbiota:
Lefty-Loopback test failed for all boards, on all computers.
Cyberbiota,
Be sure you are doing it correctly.
I have vested interest in what happens.
I am having VERY SIMILAR problems to you.
Though my boards pass the loopback test.
Just to be sure:
With the board unplugged jumper 0 to 1 and jumper RESET to ground. (Sorry can't give pin numbers on the last two)
On the PC, load your IDE (or terminal program).
Plug the board into the USB and then set the com port and start typing.
You should see what you type come back to you and you should also see the LEDs on the Arduino flash.