Continuity mistake: When George is talking to two elderly neighbors there is a mailman in the background dropping off a letter in a mailbox. A fraction of a second later he is already walking in the middle of the road.
Deliberate mistake: In the beginning of the film with Coleen after George gets up, also in several other "morning" shots, the sun is always shown near the horizon or reflecting off the ocean. On the west coast this would make this the evening.
Continuity mistake: In the scene where Sam and George are tearing down the shack together for the first time, we see the wall of the house completely intact, then one shot later, the entire bottom quarter of it is gone with only one light hit of a sledgehammer.
Continuity mistake: When Georges takes a seat at his boss's office he hangs his jacket over the back of the chair. After he sits down he picks up the jacket again from somewhere in front of the desk where he didn't put it before.
Continuity mistake: When George is crushing the models at his former workplace the secretary asks him to see his boss. He reaches out for the model he wants to keep. In the next shot you see that he isn't picking up the model at the side he was reaching for.
Continuity mistake: In the scene where Josh falls off the roof of the house being built, the fall takes place around the middle of the day, based on the shadows. Yet when the ambulance takes him away, the sun has almost set.