This one threw me for a couple minutes. Glad I didn't quicksave afterwards. Sadly I didn't think to get a screenshot at the time, but I did have a save that let me pop back to get a shot of the area and the terminal.

Anyway, very late in the game, there is a laser wall that you need to get past. When you use the terminal to deactivate it, it says that the barrier will stay down unless a counter-code is entered. Sure enough, a technician on the other side will reactivate it, so you have to kill him. Do not disintegrate him (EMP or Plasma rifles), or the game will act as if he's still there, making the barrier impassable. Using the grenade or rocket launchers is okay, though I don't know about cooking him with the UV Rifle.