Arduino Mega ADK Serial.print stale data issue

Projects Interfacing w/ Software on the Computer
3

The header is in the receiver code (so I can pipe it into a file just like that), and should signify the point where my PC is ready to receive the data.

The code on the Mega ADK is this one: sketchbook/Thermocouple5.ino at master · imrehg/sketchbook · GitHub

The receiver code is something like this in Python (with just the relevant parts shown):

dev = serial.Serial('/dev/ttyACM0', baud, timeout=1)
print "#HotJunction(C),ColdJunction(C)"
while True:
    print dev.readline()

I got around the problem a bit by throwing away the first 50ms data or so:

dev = serial.Serial('/dev/ttyACM0', baud, timeout=1)
delay = 0.05    # seconds
finish = time.time() + delay
while time.time() < finish:
    dev.readline()   # just reads but not prints
print "#HotJunction(C),ColdJunction(C)"
while True:
    print dev.readline()

In this case the buffer is received but not printed first, then later started to print the real (new) data.