(at around 1h 25 mins) When Nigel and Andy are toasting for Nigel's new job, they're each holding a glass. In the next scene, Nigel has no glass but Andy is still holding hers, then the camera shifts and Andy is holding both glasses.
(at around 27 mins) When Emily is pulling faces listening to Andy going on about how her father is visiting town and might take her to see "Chicago," the same pair of extras walk in the corridor behind her, twice within seconds and each time from left to right.
(at around 14 mins) When Emily is showing Andy "the Book," Andy is clearly seen taking out her keyboard from the desk. When "the Book" is laid upon the desk it is gone. The keyboard pops in and out between scenes.
When Andy goes to the fashion party on Nate's Birthday her hair ornament is a white butterfly, but when she finally gets home it has changed to a white flower.
(at around 28 mins) When Andy is having dinner with her father, his glasses are on/off between shots.
(at around 1h 40 mins) When Andy meets with Nate near the end of the film, he announces he is going to work as a sous chef at The Oak Room in Boston. The Oak Room was located at the Fairmont Copley Plaza in Boston and was retooled into the Oak Long Bar + Kitchen in 2012. At the time of the movie's release, it was still known as The Oak Room.
(at around 1h 35 mins) When Miranda calls Andy in Paris, Andy looks at her T-Mobile sidekick and it's ringing. The phone shows Miranda's name and under it, it says, "Connecting." For it to say that, Andy would have had to call Miranda and her phone wouldn't have been ringing.
(at around 1h 1 min) As the scene starts with Andy looking out the car window as she is arriving at the Benefit party, you clearly see the auto lock on the window sill go down indicating the car has only just started moving rather than just arrived after being driven some ways.
(at around 1h 40 mins) At the end of the movie when Andy sees Miranda coming out of the building and getting into her car, Andy is walking on 49th Street, traveling east from 7th Avenue toward 6th Avenue. In the next shot, she is walking south on 6th Avenue, crossing 50th Street (Radio City Music Hall on the corner). She would have had to walk east on 49th Street to 6th avenue, walk north on 6th Avenue beyond 50th Street and then turn around and walk back south.
(at around 37 mins) Andy is seen entering the Spring Street 6 train (subway) uptown on a train that says downtown only. Immediately after this in the same sequence she is exiting the 51 Street 6 train downtown stop. This would have been impossible on two fronts, since she would not be able to get uptown from Spring Street to 51st on a downtown train and furthermore surely would not have exited at the downtown stop at 51st street if coming from Spring.
(at around 40 mins) As Andy is distributing Miranda's unwanted items, Miranda calls; once Andy gets the phone from the others, she is talking on the Sidekick upside down. You can clearly see the multi-directional pad which is the earpiece.
Miranda accuses Emily of being an "incubus of viral plague". She should've said "succubus", which is female.
Anne Hathaway's hair is constantly changing, within the same scene. It's not just the hairstyle and cut, it's also the color. For example, when she talks to Simon Baker and he tells him he is 'desole' about her breaking up with her boyfriend, her hair is a natural-looking shade of brown; she leaves that party to go back to Miranda's hotel room and her hair is dark red. She sits down to speak with her and her hair is yet another shade of brown. She leaves her room and her hair goes from side-swept to full bangs and changes yet again from red to brown, back and forth.