The gum can be seen in Martha's hair before Inga puts it there.
Martha turns the TV in her office off twice when Walter walks in.
Sudden switch from day to night when Whitman is outside the window at Martha's parents' house.
The candles that the wind supposedly blew out are lit soon after.
At the end of the movie when Ellen and her friend ride off into the sunset, a shadow is visible under them and their horse, indicating that the sun was directly overhead.
Martha's father says "This is the best goddamned gazpacho I have ever had ever tasted." The line was "ever tasted" and he accidentally said "ever had"; the director opted to leave in the flub.
When the store owner runs after Martha with a baseball bat when he catches her stealing beer, he hits the car with the bat as she drives off; immediately it's obvious that the bat is bent--and not a real bat.