Really a minor problem and does not affect game play, but there is a mistake in the Civilopedia involving the Abbasids of the Middle Ages Conquests. The Entry and Victory screens show the leaderhead standin of Mursillis of the Hittittes but the Civilopedia uses the Arab leaderhead. For the record the game also uses the Arab king pieces as well. In the Civililopedia the Arab leaderhead is used twice as is the Mongol leaderhead.
As mentioned before, Western Church is unlocked but not useable until after researching horseback riding and castle building. This is for civs such as Germany, France and England. I have found that the same is true of the Arab civs only this time it is Arab learning that is only useable once you reach the new age. However, Byzantines and Viking civs do not have this delay because their civ specific research starts in the first researchable era or "Viking" era. The other civs must wait for the middle ages.
As mentioned before, Western Church is unlocked but not useable until after researching horseback riding and castle building. This is for civs such as Germany, France and England. I have found that the same is true of the Arab civs only this time it is Arab learning that is only useable once you reach the new age. However, Byzantines and Viking civs do not have this delay because their civ specific research starts in the first researchable era or "Viking" era. The other civs must wait for the middle ages.