THE CATHOLIC CHURCH: A SHORT HISTORY by Hans Kung, Pp.60-61:
Under Justinian, of all emperors, Pope Vigilius presented such contradictory theological viewpoints in the face of the heretical monotheism at the Fifth Ecumencial Council, in Constantinople, in 553 that he lost all credibility. Later he was not even buried in St. Peter’s, and down the centures was ignored even in the West.
Pope Honorius I was even worse. At the Sixth Ecumenical Council, in Constantinople, in 681, and then also at the Seventh and Eighth Ecumenical Councils he was condemned as a heretic; this was confirmed by his successor Leo II and by subsequent Roman popes.
Historical research, notably that of Yves Congar, has shown that down to the twelfth century, outside Rome the significance of the Roman church was not understood as a real teaching authority in the legal sense (magisterium) but as a religious authority, which was given with the martyrdom and tombs of Peter and Paul. No one in the whole of the first millennium regarded decisions of the pope as infallible.
m e a n d e r s 
you make a good pt, but as i have discussed this with an RC friend in the past, the response is slick: Papal infallibility only applies when he is speaking on matters of morals and faith. this limits things very much.
however, it doesnt mean there isnt contradiction even still. google Unam Sanctum. it was a papal bull in the 12th century. read the document for yourself. its pretty short.
basically, it claims that all who dont acknowledge the Pope as their authority are damned. so much for Vatican 2. (or many other Popes besides, even Benedict didnt say there is no salvation for those who didnt acknowledge the Pope).
peter