Amanda Seyfried, Josh Hartnett Credit: Barry King/FilmMagic, Stephen Lovekin/Getty Images

So much for a "Big Love."

After dating quietly since January, Amanda Seyfried and Josh Hartnett are now "cooling down," two separate sources tell Us Weekly.

"She's kind of a super clingy girlfriend and he doesn't want that," one Hartnett insider tells Us. "He really likes his space and she wasn't happy about that." Though the source admits they're "not totally done" just yet, "they're definitely cooling down on his terms," the pal reveals.

A second source close to Hartnett, 33, counters that Seyfried isn't the issue, and that the Les Miserables star, 26, "keeps him guessing, which he likes." Instead, the issue lies with the actor's playboy ways.

"His pattern is to get tired of girls. They were really hot for each other for a while, but she had to go to London for Les Mis [filming] and she's been there for months," the source shares. "He went to visit a few times but they just didn't end up caring enough to work that hard for it."

Still, "They might hook up when she's back in town," the insider adds. "He thinks she's fun and interesting."