westfw:
Which 1284 core are you using? Do you have the fuses set properly to use the 16MHz external crystal?57600 is a particularly problematic bitrate for a 16MHz AVR, though with a crystal you should be within specs, usually. Try using "Serial.begin(57601);"
Problematic for a 16MHz avr? Looks like "problematic for a 16MHz Arduino" is more accurate - from those comments, it looks like a "backwards compatibility with a screwup that shipped" thing?