(at around 15 mins) When Karen enters the house for the first time, it is clear that she doesn't remove her shoes, yet when Emma grabs at her ankle a couple of seconds later, her shoes are suddenly off.
(at around 21 mins) The message Susan leaves on the answering machine is a little bit different when Karen first hears it than when the detectives hear it again later in the movie (at around 37 mins), and when we actually see Susan leaving it.
(at around 1h 26 mins) At the end, before Karen enters the morgue, she has a lot of blood and bruises in her face. Seconds later, inside the room, she appears with less blood than before, especially on the right side of her face.
When Karen is in the shower shampooing her hair and she feels the hand on the back of her head, the shower is running., yet, when she spins around the shower is no longer running.
(at around 29 mins) The amount of liquid spilled from the ramen cup varies between shots.
(at around 57 mins) When Karen is in the shower, after the hand comes out of her head, she spins around in the shower stall and you can see the black tube top/strapless bra she is wearing.
(at around 56 mins) After Karen sees the ghost image in the bus window, her head and reflection do not match.
(at around 59 mins) When Karen is searching the net, she is on "www.tdn_japan.con" [sic]. This address wouldn't work. Also the Google bar spells "Imaegs" not "Images".
[director's cut only] Due to an added shot at the end of the opening scene, it begins fading to black twice.
In the first scene with Yoko, you can clearly see a crew member in the background.
(at around 10 mins) At the cemetery, Karen tells her boyfriend that burning incense is a Buddhist ritual, and that the smoke carries their prayers to the spirits of the departed. Buddhism doesn't acknowledge everlasting spirits. It is actually a Shinto ritual.
Maria describes her husband's suicide as him having thrown himself out a window. He actually jumped off a balcony to commit suicide, not out of a window.
(at around 59 mins) When Karen is looking up information about Toshio on the internet, the search engine option "images" on The Daily News Japan website is spelled "imaegs". Also, "option" is supposed to be capitalized like "View", "Tool", and "Help" are. "Tool" is also meant to be "Tools".