When Gina wakes up and sits on the edge of the bed you can see she is topless. if you look closely you can tell she is wearing panties, and still appears to be when she leaves the room. When the camera goes to show her walking through her house her naked butt is visible, so what happened to the panties?
In the beginning of the movie, when she is examining X-rays, she shows her assistant a case of Situs Inversus. This refers to people who are born with one or more organs reversed in position. She states that the condition is very rare, occurring only once in every 1000 births. In truth, Situs Inversus occurs once in every 10,000 births.
Several takes of the slow-motion car crash sequences were apparently made, and they are not the same. In one sequence the right side mirror of the Jeep is seen to flip forward and disintegrate under the force of inertia. In the other sequence the same side mirror wobbles slightly, but remains in position and completely intact.