Factual error: When Chuck is stapling fliers to the telephone poles, the tree behind Vanessa has changed colors for Fall, but still has a lot of orange leaves. The scene takes place after Christmas. In Pittsburgh, PA, the leaves are long gone by December.
Other mistake: When Lawrence and Janet are on the way to the airport and going through the tunnel, the taxi is on the wrong side of the road. This is apparent when there is a shot of the taxi, because the double yellow lines are on the left side of the screen (passenger side of the vehicle).
Continuity mistake: At the beginning, a card falls out of Lawrence's manuscript. It lands at an angle in relation to the desk. When he picks it up, it is straight.
Continuity mistake: After having sex on their 2nd date, Lawrence and Janet are talking in bed. Her arms move instantly from over her head to her side.
Continuity mistake: When Lawrence first wakes up in the hospital when Janet walks in, the guard rail on his bed is down. It's up in the next shot. Then it's back down when Janet leaves.