Hmmmm, not sure what to make of that...Could there be a blockage of some kind in the brake line? Might want to check the MC, to make sure it's not clogged or something.
Try going backwards thru the brake lines, and make sure everything is connected correctly, and no blocked. Other than that, I don't have much for a suggestion. Did you tighten the fronts before letting the backs bleed? Could be the fluid is taking the path of least resistance...ie the fronts.
Good luck,
Erik
