The fortune cookie Janet receives says "Kill your neighbor and you'll go free" on one line of text. In subsequent episodes, the fortune is in fact written on two lines of text.
When the abductees create fire and the elevator arrives, it comes to the 4th floor. Later that evening, when the night manager shows them the register, they are all listed as being on the 6th floor.
A Marine is never referred to as a "soldier".
Marine's uniform never has unit patches or flags on their right sleeve. Neither do they have their chevron insignia on their shoulder.
Marines do not wear white t-shirts under their cammies. They were switched to green in the 70's.
Sgt McNair's uniform is not Marine Corps regulation. He's wearing stripes from a khaki service uniform on the sleeves of his camouflage uniforms, instead of the small black collar insignia that he should be wearing, and the American flag patch on his upper right sleeve is backward; the field of stars should be forward on the sleeve (depending on which sleeve it's on), with the stripes flowing behind, as if the flag were being carried into battle. He's also missing the USMC "eagle, globe and anchor" symbol that should be imprinted on upper left-hand pocket of his camo shirt.
Although the indicator above the elevator in the hotel lobby shows six floors above the lobby, the exterior shots show there are only two floors above the lobby.
When the abductees first exit the Downtown Hotel, someone can be seen walking across the scene at the street. That person then stops just in shot on the right side until the scene changes.
(at around 20 mins) Outside the hotel, a crew member can be seen in the distance moving to the right and then standing still for the rest of the shot.