In the first scene with Josh Hartnett and Harrison Ford, where they are at the club's murder scene, Josh's hair is first swept over his forehead, and then, the next shot shows it's not. Then a few shots later, it is over his forehead again.
When Harrison Ford is walking through the old guy's mansion, there is a shot of them walking down a hallway. This is the same shot (and house for that matter) that was used in the movie Fletch when he was talking about how Hopalong Cassidy used to live in that house. The front of the house with the fountain in the middle of the circle driveway is also recognizable.