Adam Brody and Rachel Bilson have reportedly hit a rough patch. The stars of "The O.C." fell in love while working on the show, and it "looked like they were on their way to getting engaged just a little while back," a source told Star, but "are going through a really difficult period right now."

One reason, according to the insider, may be because of Bilson’s friendship with Zach Braff, her co-star from "The Last Kiss." "Zach calls Rachel a lot and they talk on the phone like girlfriends," says the insider. "But what really eats away at Adam is when Rachel starts talking about how mature Zach is. No guy appreciates his girlfriend comparing him to another guy." . . .Hello!

I LOVE Adam and Rachel together