When Kenya leaves the ball to go to Brian, her white dress is hanging out of the car. When she arrives at the garden, her dress is dragging in the dirt. Later, when they return to the ball, her dress is clean and wrinkle free.
When Kenya and Mark are driving back to his house after dinner with her family, the front of Mark's car doesn't show a license plate but when the car is pulling into the driveway a license plate appears.
Right after the Starbucks incident she arrives at a party with her friend. They enter the party and are offered Champagne, the waiter only has two glasses on his serving plate but on the next shot he has four.
When Brian begins to paint Kenya's toenail, the first shot of the foot before the close-up when he polishes the big toe is clearly a different foot. The toes are mangled and the big toe looks like the toe nail is mangled as well. Then when they cut to the close-up, it is a different big toe that he polishes.
At the beginning of the film, Kenya wakes up her PC, which is clearly a Dell, but it's running Mac OS X. The screen shows the telltale Finder icons on the right side of the screen and the desktop picture is one of the images that ships with OS X. A few shots later, the closeup of her calendar also shows the three "gel buttons" in the upper-left corner.