During the fight with Vivian and she has the laptop cord wrapped around his neck, Spencer is holding the Glock with the top of the slide and ejector facing away from him. But when he fires the shot that dislodges the horns, it is facing toward his neck.
When Spencer points the Glock at the head of his friend after the fight and the friend is taped to the chair and after they get done talking about the dog you hear the sound of a hammer being cocked. There is no external hammer on a Glock pistol so it cannot be thumb-cocked.
The license number of the Escalade as Jen drives away from Spencer's office is DY2702. When she swerves to avoid Olivia's Mustang it has changed to JW1826. After Jen hits the Mustang, the Escalade's plate is back to the original number and the Mustang has the JW1826 plate when it explodes.
The dates are not consistent throughout the movie - Mr. Kornfeldt can be seen reading a Wall Street Journal from June 3, 2009 (with the headline "Congress Helped Banks Defang Key Rule"); the overnight package Spencer receives from Holbrook is delivered on "29APR10"; when Jen and Spencer are looking through Henry's computer (supposedly on a Saturday) the day and date can be seen on the screen to the 17th and a Friday; and the fliers the Baileys are passing out advertising the block party indicate that's it's on the Fourth of July.
Jen's white "cute dress" in the club has a looser fit than when she and Spencer get to the hotel room and as the day goes on clothes either hold their shape or get looser not tighter, but the fit is obviously different.
When Spencer and Henry are chasing each other around the construction site the orange mesh fence caught on the bumper of Henry's car moves from covering the bumper and the lower part of the hood to up on the back part of the hood near the windshield and then back down to cover the bumper again several times.
Levenaux's destination is shown on the CIA computer to be a "private landing pad" in Nice, France. But the given coordinates (43° 42'05 N, 7° 15'05 E) are actually an address about 15 km from Nice - 73 Chemin de la Prairie, 06790 Aspremont, France.
When Spencer and Jen pull into the construction site, the tailgate of their truck is dragging behind them. When they leave, the tailgate is gone. But during the chase, just before Spencer crashes the truck through the bags of concrete, you can see it detach from the cable it was dangling from.
The "dossier" for Jasper Levenaux on the CIA computer at the beginning of the film reads "After years of paltry assistance, the United States last year provided $67 million in counterterrorism aid for training, intelligence and equipment. Assistance will more than double this year, Gen. David H. Petraeus, head of U.S. Central Command, said Friday in Baghdad before visiting Yemen the next day." Which is taken from a January 3, 2010 article in the Washington Post about Al-Qaeda in Yemen.