Continuity mistake: When the guys are looking at Andie's purse on Ben's desk, the two handles are sticking straight up but the close up shot shows the front handle folded over, and then the next wide shot shows them both up again.
Continuity mistake: In the scene where Ben just ran down the fire escape to Andie, she walks away waving. In the shot of her front side she's waving with her right hand, and then in the next shot (a rear shot) she has her left hand up. (01:08:38)
Factual error: In the very first scene in the film when the magazine covers are flashing up, the very first one has a headline which says "loose that belly". For a film whose title has the word "lose" in it, you'd think that they could spell this properly.
Continuity mistake: When Andie brings the dog into Ben's office, Ben, Thayer and Tony are standing around listening to Ben complain about how Andie is driving him crazy. Tony is holding a white mug with black writing on it, and he hands Ben a plain black mug. Just as Andie walks in, the shot changes to her, then back to Ben and his friends. However, now Ben has a gray colored mug and Tony has a black one. (00:50:15)
Continuity mistake: NBA Finals-Game 1. Andie wants Ben to buy her a Coke. During this scene, the camera cuts back and forth between Andie and Ben, and the basketball game. When Ben first looks at the game clock there is a little over a minute left in the game. He rushes to get her soda, and when he gets back, she says she wanted Diet Coke. There is a shot in this sequence where the camera is filming the basketball action, and you can see the game clock with over 7 minutes remaining, even though they are supposed to be nearing the 30 second mark. (00:33:35)