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).
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.