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By donnied11
#117209
unmonitored serial coms, when using Ubuntu Linux, would lock up the usb serial TX and temporarily brick the Uno. A thread on this is at the arduino forum here:

http://www.arduino.cc/cgi-bin/yabb2/YaB ... 86088093/0

Follow instructions at comment #34 to flash the new firmware and fix the bug:

http://www.arduino.cc/cgi-bin/yabb2/YaB ... 8093/30#34

How to put Uno into DFU mode without soldering can be found here:

http://www.arduino.cc/cgi-bin/yabb2/YaB ... 2838/10#10

I am a week into playing with Arduino and Uno and the instructions worked for me like a charm.