Audio problem: Near the beginning of the movie, while Selene is looking at the CCTV video from outside the subway station, Kraven enters the room and talks to her. Throughout their conversation, the sound quality of his voice changes as he walks away from where the mic is located (by Selene).
Continuity mistake: At the end when the 3 vampires are shooting at Michael, Selene drops behind them. The blood on the left side of her head disappears and reappears a couple of times. When she's taken them out it's back again. And it gets bigger and smaller all during the time it's there.
Revealing mistake: When Selene is firing her guns in the floor making a circle of holes so that the floor collapse, you can see in some shots the angle of her guns are pointing all kinds of directions. Instead of making a perfect circle the holes would be spread around the floor and the bottom of the walls in the hallway.
Continuity mistake: In the first scene when Rigel is crouching, taking pictures of the werewolves, he is holding the camera in his right hand just as he is about to jump down. However, when he is jumping, the camera angle changes and it can be seen that he is no longer holding a camera in his right hand.