Factual error: Every time the silver nitrate is shown on clothing, it is shown as silver. Silver nitrate in fact is black once exposed to light.
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: As Lucien reprimands the Lycans for their pit fights, of the two Lycans who were just fighting and were naked during that fight, on the taller one the top seam of his underwear/pants is visible.
Continuity mistake: When Lucian goes flying over Selene's car, in the overhead shot we see that the road below him has large parts with visible concrete because there are no paving stones. But in the next shot, a close-up of Lucian landing on his feet, the road is fully paved with paving stones.
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.
Revealing mistake: In the end fight scene between Viktor and the hybrid Michael, Viktor picks Michael up and throws him into a stone column. Terrible wirework then comes into play: Michael travels far too slowly towards the column for someone who was just thrown, he makes one perfect spin in the air on his way, and when he finally connects with the column, it's a delicate bounce off before the wire drops him on the ground. His legs don't even move from the "impact".