Did Justin Timberlake Cheat on Jessica Biel w/ Olivia Munn?

Singer turned actor Justin Timberlake made his way out with actress girlfriend Jessica Biel for breakfast in the TriBeCa neighborhood area in Lower Manhattan, New York on May 5, 2010. Jessica flashes a smile towards the shutterbugs as Justin pulls her along in a rush to get out of the spotlight. Fame Pictures, Inc

Justin Timberlake allegedly cheated on Jessica Biel with Olivia Munn in September. Justin & Jessica seem like a great couple but they don’t comment on their relationship which I think explains why we speculate so much about them. Do you think Justin cheated?

Justin Timberlake cheated on Jessica Biel with actress Olivia Munn during a three-day fling this past September, reports the new Us Weekly (on newsstands now). Timberlake, 29, and Munn, 30, a Daily Show correspondent who stars in the upcoming NBC series Perfect Couples, first met at a Sept. 26 MySpace event. After exchanging numbers, he “started chasing her

LOS ANGELES - OCT 16: Olivia Munn arrives at the 2010 Environmental Media Awards at Warner Brothers Studios on October 16, 2010 in Burbank, CA Photo via Newscom

immediately,” says an insider.Munn resisted his advances, telling him it was a no-go if he was still with Biel, 28, the source tells Us Weekly. But Timberlake “has been telling people it’s over with Jessica, even though “the reality is he’s just doing it behind her back.”

Believing he had left Biel and that her relationship with Timberlake might develop into something serious, Munn took him to her hotel, the Gansevoort Park Avenue NYC, Sept. 27 and 28, where “they were openly affectionate,” the insider adds.

The insider tells Us the two “had amazing sex” that night.