Diptychs were of course the lists of bishops considered Orthodox, but these lisrs were often not up-to-date and not too many people were concerned about that.
One thing that everyone must bear in mind is that after 450 AD the Church essentially existed as two separate communities because of the language divide.
While officially, Rome was still one state, there was very little communication between the Greek and Latin wings, as the majority of people, even bishops didn't understand each other.
The issue that started the freefall was, of course, the invitation of the Franks to Bulgaria by the Bulgarian khan, Boris, who was shopping for a "better" church. This was not uncommon evn when the communion was effectively broken. For example the first Serbian king, was crowned by the Pope in the 12th century.
It was the Frankish teaching of the filioque to the Bulgarians that resulted in Greek reaction and the ventual expulsion of the Franks. The Franks then in turn accused the Greeks of "heresy" for "omitting" the filioque (shows you how little people knew of the Councils and their decisions -- in other words: nothing!). The Frankish king himself was semi-iconoclastic by the way. Political realities, however, forced the Pope to look the other way and use the situation to his advantage.
Kosta correctly points out that a rough ending point to the era where bishops in the East and West fully understood and agreed with each other was the 5th century.
The changes that happened in Western theology were mostly potential ones until they became linked with secular political ambitions of the Franks in the West in the 8th and 9th centuries, and they did not take place without resistance by what Fr. John Romanides calls the "West Romans," whose phronema was still identical to that amongst the "East Romans."
Whatever one calls them, there were individuals and forces in the West that did not embrace the new way of doing theology that primarily grew out of unbalanced (unbalanced by the teachings of other Fathers, that is) appropriation of some of St. Augustine's more speculative works. It isn't as though the East didn't have its own speculative works that were outside the pale -- they were just sidelined either as outright heresies or as personal speculations that were not accepted as part of the "consensus patrum."
For a number of reasons (and one of them was definitely the situation in Bulgaria that Kosta mentions), these two very different world-views first became fully aware of the existence of the differences between each other in the 9th century, and the clash was unmistakable. The conflict never really completely came to an end, and the Schism took place on a continuum (and with fits and starts, ebbs and flows), depending on where one lived in Christendom, from the 9th to the 12th centuries.
For example, B16, in his writings on liturgical art in the West, shows an understanding of this when he wrote (as then Cardinal Ratzinger) that the West has never fully come to terms with the 7th Ecumenical Council and has never made it its own. Thus, when Kosta points out the semi-iconoclasm of the Frankish rulers (and key clerical advisors), he is not making this up. The 7th Ecumenical council was in the 8th century (although the final defeat of iconoclasm in the East took place in the early 9th century), so by a rigid theoretical application of "Schism = 1054", there should have been full understanding on the theology of iconography between East and West, but there most obviously wasn't.
Right now, though, the most pressing problem is the one that jec1ny mentions at the end of his post:
Namely the problem of rampant liberalism and open dissent, so serious, that in some places clergy and even bishops who are Catholic in name either secretly or openly are in favor of making changes in the doctrines of the Catholic Church that would be much more in line with Protestantism. Many of these changes, such as the ordination of women, the acceptance of homosexuality, and a more tolerant attitude about abortion would certainly be unacceptable to the Orthodox. These issues by and large do not exist within the Orthodox faith. So to some degree the Pope will need to preserve his authority to reign in clergy who are straying dangerously close to what both the Catholic and Orthodox churches would call heresy.
I know that in my own city, while we Orthodox have very nice and cordial personal relationships with Catholics here, you would have a hard time convincing our parishioners (and we all attend one "middle of the road" parish that serves every possible ethnic group) that we share a common faith with the (quite liberal, but not atypical for America) Catholic churches here, and you would have a hard time convincing most Catholics here that they have more in common with us than they do with the local Lutherans and Anglicans.
I am one Orthodox who is holding out hope that B16 will set changes in motion that will make that less true some decades down the road. I know that I have been told my more devout Catholics than I can count that they hope we don't reunite, because they are afraid that the Catholic church as it now is would only infect and hurt us. A common theme amongst them is "we Catholics need to get our house in order first."
I think that Kosta's estimation of needing at least a century to prepare for any kind of council of reconciliation is not at all overstated.
We have had some frank discussions on the filioque and the Immaculate Conception on recent threads in which I think that those who choose to remain calm are both realizing those points where they misunderstand the position of the other -- and soberly also understanding (as annalex pointed out in her #12), that there are significant differences in worldview and the approach to "doing theology" that cannot be resolved through ambiguity and finesse of terminology.
A failure to recognize that will only lead to another Council of Florence, where Orthodox laity and common clergy reject any agreement hashed out by hierarchs. I suspect, as does Kolokotronis, that B16 has far too much insight into the patristic mind to attempt any unions that are not based on fundamental and organic agreement. I suspect that he also realizes that his primary task ahead of him to make this happen (as David observed) is to inculcate a new spirit in RC clergy and laity, and that encouraging them to have contact with Orthodoxy will promote that.
Anyway, those are my (not so brief, after all) thoughts. If I have given offense to anyone, please forgive me.
While officially, Rome was still one state, there was very little communication between the Greek and Latin wings, as the majority of people, even bishops didn't understand each other.
It also didn't help that the Latin west was mostly under the thumb of pagan or Arian German tribes after that point.