Assassins Creed Tips, Help, Tricks, Hints Cheat Codes and Strategy

Hey guys, what is the story with "Error - memory sector unavailable" outside Acre. I have completed the game many times, 980 out of 1000 - didn't do the annoying conversations with Lucy for the last 20 pts.

Just before you enter the city of Acre, on the left past the fence where the scholars come from, go to the wall. It is blued out, unavailable just like I needed to complete a memory.