(at around 26 mins) When Trish enters Jake's room, the floor in front of him is empty, and the camera turns to face Trish. When it's put back on Jake there is some kind of sport equipment on the floor.
(at around 1h 8 mins) When Aubrey goes into the dark room and picks up the picture, the picture should be black. It was in the developer last. It would have had to go into the stop bath to stop developing, and then the fixer to not go black when it was exposed to real light.
(at around 1 min) Trish, under the influence of The Grudge, hits Bill, her husband in the head several times with a frying pan. In close scenes, the frying pan is a heavier cast iron model. However, when the pan is showing in closeups it's a much lighter non-stick model. While this would be very painful, the pan being as light as a nonstick unit, would have not been fatal as the film portrays it as being.
(at around 57 mins) When reading the diary, the characters read the book left to right, like a book written in English. Japanese, when written in tategaki format (top to bottom) or yokogaki (left to right), still is opened and paged right to left. However, the characters correctly read the printed book in the same scene.
The goof item below may give away important plot points.
(at around 1 min) When Trish comes into the kitchen in the opening scene, the clock on the wall is 8:31. In the close-up of her hitting her husband, the long hand of the clock has moved, making it 8:35, then as she sits down, the clock is once more 8:31.