chucktodd:
The wiring_analog.c in the Arduino core will accept either '0' or 'A0'. the 'A0' constant is defined by the pins_arduino.h depending on which variant you selected.
Right. Not to beat a dead horse, but my point (apparently poorly made) was that MAS3's supposition, that the code might be "using pin 0 (serial Rx)...that's asking for trouble," was not correct: the code uses analog pin 0, not digital pin 0 (serial Rx). So that can't be the source of the problem....