When Alida tells Cary to get her coat, Cary gets her coat, but doesn't stop to get boots. But when she gets out of the car at Ron's mill house, she's wearing boots.
We first see Cary drive a 1955 two-door Lincoln but several scenes later she is driving a four-door Lincoln. It is possible that Cary, a recent widow, still had both the car she normally drove as well as her late husband's. This would account for the two different cars.
Cary reads two quotations from the same page in Walden: "The mass of men lead lives of quiet desperation" and "If a man does not keep pace with his companions..." Those two quotations are from opposite ends of the book, the first and last chapters, respectively.
When Ned mixes a large batch of martinis, the liquid in the shaker is light brown, even though he makes a point of saying he used only two drops of vermouth, which would result in a clear-colored drink in a shaker that big.
When the deer runs away, a crew member can be seen hiding behind the automobile.
When the door to the butcher's shop is opened, the camera and some crew members are clearly visible in a reflection.