I heard there were a lot of bugs in this game, but this one finally got me. (spoilers). In playing the game, I saved every other slot  just in case my file was corrupted like my friend's was. That way I would always be one save behind my most current one. Note, save a third file every fourth time, really!
This is what happened. I just got to the second map and delivered the weapons barge into the central city. I escaped the ensuing battle and got the call from Builder saying that he needed my help over at the marina. So I zip across the lake to help him out. When I get there I man up and take out all the enemies. Yay, I saved the day... No! Builder is supposed to be in the bridge of the ship, but instead he standing on lower port deck. When I go into the bridge he starts talking to me, but just a sentence. Mission Not done, because the map says I have to go talk to him on the bridge... Wait, he isnt on he bridge. So I go down to the main deck where he is standing and the action/talk button comes up. I click and nothing happens. Aparantly you can't talk to him unless he is on the bridge, but he isnt. I loaded my last save, and even the one before that and the same thing happend. I was so pissed because the third save back I was only 16% completion. I went and got all the damn diamonds on the first map and now I cant even move past this mission. Fuck! Does anyone know a way around this, like can I go to another sub mission even if I dont finish this one?