I am seeing negative latencies of up to 1 second. I am using ntp to synchronize both machines at an interval of 2 seconds, so the clocks should be very much in sync (and are from what I have observed). I agree that it is probably OS, perhaps I should hop over to a Microsoft newsgroup and pose the question, although I'm sure they will find a way to blame it on Python.
-- http://mail.python.org/mailman/listinfo/python-list