After successfully killing the guards and soldiers in the generator room and activating the third primer I am told to go to the crane. The only door available leads me by some elec tubes and a door at the end. The only thing is once I go through this door onto the platform there's no were to go. Both the gate on the left and on the right and shut and won't open no matter what I do. I have reloaded the checkpoint, the game even the box and still get no where. Any one got any ideas.