I tested with the serial monitor, Pure Data and Processing. I also switched boards with the same code. The Duemilanove runs the code fine, the Arduino Uno does not.
Here are some more strange results (when using Arduino's serial monitor set to the proper baud rate) with the Arduino Uno and the same code:
When I type "a" (send)
I receive "a"
When I type "ab" (send)
I receive "ab"
When I type "abc" (send)
I receive "abì"
When I type "abcdefg" (send)
I receive "ab,V–"
If I switch the baud to 115200 in the code AND in the serial monitor, all the messages sent are identical to the ones received. There definitely is a problem with 57600.