In a romantic scene in the middle of the film Melsa tells Peter, that "she's had dozens of cigarette lighters but none of them worked." However, at the start of the film when she snoops around the Lane house, she uses a WORKING cigarette lighter as a torch.
When Melsa first calls the police at the beginning of the movie. The police cars are rushing to the Lane mansion. As they pass "Jones Drug Co" and "Barber Shop" the signs are backwards (mirror images).