Leonardo DiCaprio and Blake Lively: Hanging By A Thread

The tension between Blake Lively and Leonardo DiCaprio was obvious as they sat across from each other at the gastropub Father's office in Santa Monica on July 15. "They talked about their relationship extensively," an observer tells Star magazine in this week's issue.

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"All the serious talk must have gotten to Leo. He threw back a number of beers, to the point that Blake told him to slow down." Weeks before, Leo had put the brakes on their new romance, blaming Blake's "clinginess," an insider tells Star — leaving her devastated. He was soon cavorting with a bevy of babes.

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While at Beacher's Madhouse cabaret club at the Hollywood Roosevelt Hotel in L.A. on July 13, "He was surrounded by girls and clearly loved every minute of it," a source tells Star. "He seemed especially taken with one sexy brunette."

And though Leo and Blake has been parically joined at the hip since May, he took his mom, Irmelin, to the early July wedding of his close friend, producer Ryan Kavanaugh, in Capri, Italy.

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The couple's intense heart-to-heart at Father's Office seemed to smooth over their problems. "By the end," says the observer, "Blake and Leo were laughing and holding hands."

But their issues appear unlikely to just fade away. Mama's boy Leo wasn't pleased that Blake made a bad impression on Irmelin when the three dined together in June.

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"Leo told Blake that his mom thought she was trying too hard," says the insider.

FOR MORE ON LEO AND BLAKE'S ROMANCE PICK UP THIS WEEK'S ISSUE OF STAR, ON SALE NOW!