When Dr Faulkner and Sydney put Mrs Martinez in the car to take her to the hospital it is in the driveway very close to the house but they didn't park in the driveway they parked on the road and walked up the driveway to the house.
Near the beginning when Sydney pours herself a glass of iced tea, the level in the glass decreases between shots, before she even starts to drink from it.
During the scene when Sydney witnesses the fire in her apartment, a man grabs her arm and drags her forward. Later, when we see the burn marks on her arm, the mark of the man's palm is on the wrong side, as if he dragged her backwards.
During the scene where Dr. Faulkner gives Sydney her donor's information, we can see the distance between the taxi and a Fedex Kinko's office change. As the taxi is taking off, the Fedex office starts to look more distant. When Faulkner stops the taxi abruptly and makes Sydney get off it, the distance between the taxi and Fedex has shrunk considerably. This implies that the taxi went forward and then backward, when it was clearly just going forward.
When Sydney is at the Chinese restaurant, the meat that the cook was cutting is alternating between more and less cut.
In the beginning, during rehearsal, you hear music but the musicians pretended they were playing their instruments. Sydney seems to be the only one "playing an instrument".
After she gets out of the shower, Sydney and Ana's reflections in the mirror don't completely match up.
When Sydney gets out of the shower and is in the room with her sister, Sydney says "I need to find out who she is" and then her sister replies with "Who?" but her mouth is saying something else.
The music from Sidney's violin does not match her arm movement at all.
When Sydney and Paul walk over to the Mexican child to ask him about the fire, in the shot of Paul talking to him, you can clearly see the cameraman's shadow cast on the ground to the right.
When Helen drives Sydney home from the hospital, the camera outside the passenger seat window is reflecting in Sydney's sunglasses.