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By Kat Giantis

What? You mean you didn't get an invitation to Jeremy Renner's celebrity-stuffed 40th birthday bash on Saturday night at his newly remodeled Hollywood Hills digs? That's too bad, because the presence of a couple of knockout, top-heavy blondes got the rumor mill a-churning.

Let's start with Blake Lively, whom the New York Post says enjoyed an extended tête-à-tête with Leonardo DiCaprio at the festivities.

"They were on the balcony together for an hour," says a source. "They were standing close in a corner and looked like there was a lot of flirting. Later, they were together again by the bar."

Perhaps Lively, who was last seen cozying up to Ryan "Hey Girl" Gosling, was just getting reacquainted with DiCaprio after joining him and director Baz Luhrmann for dinner in November to discuss the role of Daisy Buchanan in the remake of "The Great Gatsby" (the part eventually went to Carey Mulligan).

An insider insists that Blake and Leo are "just friends," and besides, the actor is still very much with his perma-bikinied supermodel squeeze, Bar Refaeli.

RELATED: Blake named face of Chanel

He rang in the New Year with his longtime leggy love in Cabo San Lucas, and they've been soaking up the sun in Hawaii this week with fellow celebs Tobey Maguire, Cameron Diaz and Alex Rodriguez, and Naomi Campbell.

And while we wouldn't have pegged the modelizing Leo as the romantic type, it seems that during a paddle-surfing session with Bar on Monday, he plucked a yellow flower from the water and offered it to her. All together: Awwww.

No surprise, then, that DiCaprio exited Renner's shindig with buddy Kevin Connolly.

Speaking of Connolly, he stuck close to pal (and "He's Just Not That Into You" love interest) Scarlett Johansson at the gathering, with the duo chitchatting with Leo and "bunch of agents," a source tells Us.

But don't get the wrong idea about ScarJo's hang-time with the "Entourage" actor, who was recently spotted in the company of Eva Longoria: He's also good friends with her estranged hubby, Ryan Reynolds.

And despite reports that the actress is "devastated" by reports linking her soon-to-be ex to Sandra Bullock, "She was having a great time," says the spy. "There was no drama with her. She was running around the party and was a party girl, bouncing around from person to person."

Those people included Charlize Theron, who also reportedly chatted with social butterfly Leo, Christina Aguilera (she was a "little wobbly," says the Post, and got a helping hand staying upright from joined-at-the-hip boyfriend Matthew Rutler), Ben Affleck and Colin Farrell.

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