Before Emily slaps Jack in the dream sequence, it can be seen, for half a second, that Jack's face is already red, when it wasn't red in the shot before. (This was because they had to film Emily slapping Jack multiple times.)
During the therapy scene, when Jack has a mental break down, Lynda gets up from her seat and comforts him. In real life, therapists are legally not allowed to touch their patients due to chances of harassment or other scandalous activity.
Credited as The Mugger, the character himself never actually robs Jack or Emily, but knocks out Jack and shoots Emily, making the credit seem very off.
During the opening sequence, when the camera pans across the photo sets of Jack and Emily, the camera man, Alex Ross, can be seen holding the camera and walking in the reflection of the glass. (Look for the wavy lanyard.)
During the therapy session sequence, a phone can be seen on the couch with the script on it.
At the beginning, Jack said Emily wanted to be remembered for her "harmony and tranquility" and the parking lot scene backs this up, yet during the dream sequence, Emily is portrayed as a bit stuck up and mean. This means that either Jack remembers her wrong or saw her differently, which makes no sense, considering Jack states that he knew she wanted to be remembered for being nice.