There has been speculation for years that Reese Witherspoon and Ryan Phillippe's marriage was on the rocks, so the announcement that the couple was going to split hardly came as a surprise. Still, why did the couple choose a time when Phillippe had a movie in theatres (Flags of Our Fathers) to break the news of their separation? According to the National Enquirer, Reese had recently discovered that Ryan had been unfaithful.

The tabloid claims that Ryan is involved with Abbie Cornish, his co-star in the upcoming film, Stop Loss. While filming in Austin, 32-year-old Ryan and 24-year-old Abbie reportedly became more than friends.

The pair were seen having an intimate dinner at a restaurant called Kenichi after the Austin filming ended on the movie. A spy for the Enquirer said, "They asked for the restaurant staff to pull curtains around their table, so no one could see them." Another witness to the dinner told Pink is the New Blog, "We sat two tables away from Phillippe and an extremely attractive blonde (not Reese. The couple had a partition placed around their table soon after they arrived, but we could still see their legs intertwined under the table. As we left, we could see them clearly making out behind the partition."

The Enquirer reports that Witherspoon discovered the affair when she saw messages to Cornish on Phillippe's BlackBerry. October 16, the night that the couple attended the premiere for Flags of Our Fathers, Reese found the evience of the affair. "When they got back to the hotel, Reese found Ryan's BlackBerry, which he'd carelessly left in the bathroom - and she read it. Ryan was caught red-handed. All he could say was he didn't mean what he'd written to the other woman," says an insider.

Ryan had to leave betrayed Reese behind in Los Angeles while he traveled to Morocco to finish working on Stop Loss. The time apart only made Reese angrier. When Ryan came back from filming Reese had decided to end the marriage. "Reese is heartbroken," a source said.