When HRG is trying to get Stephen Canfield to kill Sylar, Sylar stands at the car watching and not hearing anything. But in Season 1, Sylar killed and took the power of a hero whose talent was super hearing - he should have heard every word.
When speaking to Nathan and Tracy about the origins of their abilities, Angela refers to Tracy's twin sisters as Nicky and Barbara. However, the third sister, as seen through Season 1, is named Jessica, not Barbara.
When Mohinder is dragging the body of a drug dealer into his 'den' a trail of blood is visible from the bottom of the stairs to the entrance to his den. When he walks out of the doorway the blood is gone and reappears again when Maya looks down at the ground.
The flyer that Mohinder reads has the word "increasingly" spelled as "incresingly"
When Linderman and Daphne meet at Pinehearst, Daphne moves forward to address Linderman and we see a crewman and some cables on the ground.