Continuity mistake: Right after Charlie and Irene push the car over the cliff, Charlie asks Irene if she grabbed the wallet off the dash and she says no. Later in the motel, when they are lying in bed, Charlie is sharing family pictures with Irene and they talk about carrying pictures in their wallets. Charlie's was at the bottom of the lake with the car. [The deleted scene on the DVD doesn't really help - in it Hank jumps off the cliff to get his wallet, and then Irene follows. However the movie shows Charlie and Irene looking down the 30 meter high cliff and walking away with dry clothes. Deleted scenes can "disallow" a mistake only if they fill in plausible back story, rather than contradicting the "proper" movie directly.]
Continuity mistake: Right near the end of the movie when Irene is saying goodbye to Charlie, her makeup is a lot darker to when she is driving away in the car, it looks a lot lighter and rubbed off. When she is pulled over again by the police and gets out of the car her makeup is once again a lot darker.
Continuity mistake: The movie starts out in the present and then flashes back. The skinny trees in front of the house are tall in the beginning and in the flashback they are small. They grow a little more every time it's been a few years, but when they come back to the present, the trees are still only half grown in one shot. In the next, they are fully grown.
Continuity mistake: In the scene where both Jim's characters are beating each other at the wheel of this red convertible, bad Jim throws good Jim out of the car which was doing some 30/40 mph in a straight line. In the next shot Jim is seen chasing the car on foot: the convertible is now doing no more than 7/10 mph and it's descending a hill after a sharp right-hand corner.