I got to Chapter 10: Entanglement, now I am stuck. I'm to the part when you set up the sentry guns to kill the oncoming soliders. You can hear Alyx telling you to setup the guns, so I did. I go back to one of the storage cases where I just got the sentry gun to hide. I waited for about 3 minutes and nothing happened. I ran all over the place and there wasn't a single (alive) solider to be seen. I have played this part before but died after a quicksave. I even went back a couple of quicksaves and still the same thing happens.
Are you sure taht you have set up all the turrents? If it's the first time you have to, there should be 2 to set, in next two engagements there are three, otherwise the fight doesn't begin. If that's not the case, then you might have this problem due to simple game random bug. Load a save from level before, or open console (if not enabled, go to Option -> Keyboard -> Advanced -> Activate Developers Console), type in 'restart' and hit enter. The second option will reset the level, with possible ammunition ammount changes, although I'm not sure.
Thanks a lot. I figured it out. There 3 Sentry guns to setup. I thought I would save one for when the others fell. Just for the heck of it I setup the third and low and behold we had a fight.