Jeff Hecht says,
"There's an important thing to remember in looking at Protarchaeopteryx and Sinosauroptereyx: the fossils we have are 20-30 million years_later_than Archaeopteryx. It's possible these are ancestral forms that survived that long. It's also possible that - at least in Protarchaeopteryx - we're seeing descentants [of?] flighted birds that became secondarily flightless. This complicates the question of where the down came from."
Keep up the 360-degree thinking, Jeff. Some others seem to prefer blinders! Life is often more complicated than the black-and-whiters would want to believe.