Denver had the ball and Manning threw a touchdown pass to Eric Decker with about 4:50 left in the game. It was called back because of OPI on Decker.
It's at 5:25 in the video.
Denver Broncos vs. San Diego Chargers highlights - NFL Videos
Doesn't show a good angle, but on TV they showed replays from right in front of the play and there was barely any contact by either player. Did anyone else see it when it happened?