When Beth picks up Jenny's bloody hand and drops it back down, the close-up shows her dropping it back into the pool of blood. But on the wide shot, Jenny's hand is away from the pool of blood.
Oregon drivers licenses do not show the birth date in 17-11-1979 style, That style is Washington (where Beth is from). Oregon birth dates are 11-17-1979.
While Mark is cycling through the town, he passes a Banque d'Epargne (Savings Bank), tipping off the Quebec location.
When Beth/Karen and her boyfriend are trying to get her to predict what card he is holding, the cards in question are upside down - when the cards are flipped vertically, they are still upside down.
In the opening scene where Jenny is fleeing the school, she tells the taxi driver to take her to the airport. Yet in the next scene he drops her at her house.
When Karen is leaving the party, you can see her microphone box attached to the back of her dress.
When Beth/Karen is in the bathroom she turns off the dripping shower and we see the cameraman's reflection.
In the opening credits, you can clearly see the end of one of the steel pipes that forms the skeleton of the scary tree.
In the lecture on Catherine the Great, the name of her lover Prince Potemhin is mispronounced; in Russian should be more like 'PatYOMkin'.