So I'm stuck in the quest The Path of Knowledge.. I got to the part where you have to lower the bridges to cross by placing a control cube on one of the three pillars thing (this is in the Nchardak Aqueduct). But I could not activate any of these three! I have 2 control cubes in my inventory and nothing would happen. I tried going back the previous saves; putting one of the cubes on one of the other pillars so I'm left with one, nothing works.. Any ideas how to go around this? Thanks..