Other mistake: During the church scene, an elderly man is seen using a Black Motorola flip cell phone that wasn't available until 2005, some 2 years after the movie was set.
Factual error: In the beginning during the gas station scene, the timeframe of the movie is supposed to be Sept 2003 but a number of late model (>2006) Ford, Subaru and Honda vehicles are seen driving by in the background.
Continuity mistake: When Frida is in her room and throws the stuffed animal near the window, she sees a zombie in the pouring rain across the street. However when her boyfriend startles her in the window, he is dry and the rain and wind instantly stopped.