Continuity mistake: When Detective Rodriguez is looking in his rearview mirror at Frannie he has facial stubble in one shot and then is shaven in the next.
Factual error: In the scene where Meg Ryan and her sister are in the coffee shop, her sister calls to the waitress that they ordered a latte, no foam, very dry - it is impossible to make a dry latte without foam, because dry means "foamy." Not to mention, a very dry latte is technically a cappuccino.
Continuity mistake: As Detective Malloy dresses after going to bed with Frannie he places his pistol on his belt; he then places his backup gun in the small of his back. Shortly thereafter he picks up his backup gun from a table and leaves with it in his hand.
Continuity mistake: When Meg Ryan walks home from the lighthouse she is barefoot. As she approaches her apartment the camera shot is from overhead as she walks through her garden. From this view she is wearing sandals (same sandals she is wearing through most of the film, although during this particular costume change she wore heels before going barefoot). The next scene shows her entering her apartment, she is barefoot again.
Continuity mistake: You can see a blond girl walking by from a shot in the car. When the detective gets out, she walks by again.
Other mistake: In several scenes the Detective is wearing his shield attached to his belt. NYC Detectives do not do this, if displayed it is pinned to their outermost garment.
Continuity mistake: In the scene where Frannie and Detective Malloy are standing outside the police car, after Frannie was picked up by the two police officers, outside her apartment, you can see a girl with a white shirt with black sleeves and a very short skirt passing by. After a few seconds, Detective Malloy goes back into the car and you can see the exact same girl passing by at the same direction as before and she even wears the exact same clothes.
Continuity mistake: When the Detectives car stops in front of the Pct. Malloy's coffee cup is to the far right side near the passenger window. When he gets back in the car the cup has moved almost to the center of the windshield.
Other mistake: The detective's car has leather seats; NYPD (like most departments) would buy the least expensive cars, which certainly wouldn't have leather seats.
Continuity mistake: In the scene where Frannie and Cornelius are talking at a bar Frannie is wearing her glasses. When a glass is dropped and breaks she turns to look and in the next shot her glasses are gone, and then reappear in the next shot.