The quest called Shh on the Mars simulation causes headaches for a lot of people. Once you find the rebels you need to avoid being spotted by a wandering guard. This is currently based on your characters distance from the guard rather than line of sight. One way to complete this quest is to hide in the corner in the building to the right of the group. You can move the camera around enough to watch the guard. Once the guard has passed by, move to the bridge opposite the building you're in. Make sure the guard has his back to you when you're running across.
(*) As of patch Sep 22 2015 - v5.4.8 This quest has changed. You no longer need to hide from the Guard. Now you just need to go find the rebels . Then Just wait till the conversation is over.