[lysis]

yes several of us have had a problem where this guy walks in place instead of going and opening the gate at the beginning of the level (snowy level). I fixed it by going back several save games - getting back up to that point, and then he no longer walked in place and he managed to open the gate, and then no matter what you do he is killed.

Other people said they got it to work by not being aggressive and killing the guards, they let him come out and shoot them.