What issues divided the eastern and western christian churches?

The major issue was whether the Pope ofr the Byzantine emperor had the final authority in who appointed the Patriarch of Constantinole (the highest Church post in the east). 

The other big argument was over theology and doctrine,specifically the Filioque.This is the idea that God,Jesus,and the Holy Ghost are all one aspect of the same thing/being - accepted by the Catholic Church,but not by the Eastern Orthodox Church.

The re-election of the president abraham lincoln.