Continuity mistake: In the restaurant at Cannes, Meg Ryan stumbles backward over a dessert cart and lands with her face clearly on the floor. After a cutaway to the diners' reacting to the crash, Meg's face is squarely in a chocolate cake. Maybe she just became hungry after the accident.
Factual error: Kate and Charlie live in Toronto. When we first see them in their car, at the beginning of the movie, it has no license plate in the front. In Ontario, cars are required by law to have a plate in the front as well as in the back. While some jurisdictions may be lax in applying their two-plates law, Ontario isn't.
Other mistake: During the scene where Luc and Kate first meet on the plane and are talking, Luc gets up to go to the bathroom (the second time). When he returns to his seat, the plane has landed, Kate is sleeping, and the other passengers are deboarding. There's no way he would have been allowed to remain in the rest room during a landing.