Continuity mistake: When Nora is explaining to her friends at lunch that she and Luther are skipping Christmas, her friend asks her "When do you leave?" without Nora ever mentioning that she and Luther were going on a cruise.
Continuity mistake: Throughout the movie, the number of cars the train has changes. The scene where Hero Girl's ticket is surrounded by a pack of wolves shows the train having around 20 cars, but the scene where the train's on the ice shows it having 5.
Suggested correction: The entire journey is likely just a dream. There are many things in the movie that cannot happen in the "real" world, and the number of cars changing is just another aspect of the dreamlike nature of the trip.
Continuity mistake: Near the end, Mike is hanging the glass angel he got from Artie on the tree. Nina comes in through the front door, leaving the door chain hanging (unlatched), yet, in the very next shot the chain is on.
Continuity mistake: In the scene where Ben Affleck gets hit in the head by the shovel in the beginning, when the shovel is about to hit him, the paper is not on fire for a split second. Then when he's on the ground it's on fire again.