Revealing mistake: Watch closely in the Gus murder scene, as the vampires start surrounding him outside in the snow, notice the very first vampire "close-up" shriek, remember the face. After Marlow and Iris attack the couple in their house he puts his claw to the record player and emits a howl as the other vampires throughout the town follow suit with their own shriek, each one gets his/her own close-up, count to the fifth vampire face and you will notice it is the exact same shot used earlier in Gus's murder. (00:18:05 - 00:38:30)
Revealing mistake: In the scene Josh Hartnet's character dumps the vampire into the grinder, and gets beat up by the one who turned into a vampire, in the close-up shot of his face where he is bleeding, look at his nose. The patch make up used for supposed ripped flesh is visible. It's colored orange and is rather obvious.
Revealing mistake: After Eben dies from watching the sunrise his hair burns away and his scalp flakes, however the shadow of his hair can be seen on his wife's face.