Revealing mistake: During the heavy snowstorm, the telephone wires are still, even though it's a blizzard.
Factual error: When the vampire throws the lit match on the oil it catches fire right away. Oil will only burn at a certain temperature no matter how many times you throw a lit match on it.
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.
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.
Suggested correction: I am watching this movie as I write this response. I cannot find this mistake anywhere in this scene. Perhaps if you could be more specific with the time and actor you are referring to as neither Josh Hartnet nor Billy Kitka have anything like what you describe on their face.
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)