Continuity mistake: When Samuel L. Jackson tries to get into Niebaum's computer he lets the secretary tell him the password. The secretary tells him the code is C-I-COMG9. They type C-I-COM then when they cut back it says A014487G9. (01:22:15)
Continuity mistake: In the scene where Samuel L. Jackson is walking by the stairwell to get J.T. Walsh, the SWAT team member is not handcuffed to the stairwell, and in fact is not seen in the room. A few seconds later, as Samuel L. Jackson is attempting to push him into the other room, the SWAT member is shown handcuffed to the stairwell. (01:42:11)
Continuity mistake: In the scene at Niebaum's house you see Danny Roman sitting in front of a computer screen. Behind him Chris Sabian's plaid shirt is easily recognizable. However, in the next shot Chris is not standing behind Danny, but is at the door keeping watch. (02:02:10)
Continuity mistake: Towards the end of the movie, Frost comes out to tell everyone that Roman has been killed. We hear over the 2 way radio Sabian saying "Let's get you some help." Just before he says that, you can see in the background behind Frost that Sabian is already helping Roman out the door. Seconds later Sabian starts helping Roman out the door. (02:04:00)
Continuity mistake: At the end, the paramedics are taking Samuel L. Jackson into an ambulance. His head is toward the front of the ambulance but in the next shot, Jackson's head is at the back of the ambulance. (02:08:25)
Continuity mistake: In one scene Kevin Spacey goes up the building in a pair of dark trousers and comes down in a pair of light trousers.
Continuity mistake: At the beginning of his seizure in Niebaum's office, Danny Roman handcuffs Niebaum to the arm of his chair. In subsequent shots, the latter's right, then left, then right hand is the one shackled.
Answer: According to IMDB.com, Paul Guilfoyle did play Nathan, though he wasn't credited for the role.
Xofer