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When John Mayer isn't busy toying with the affections of Jessica Simpson and Jennifer Aniston (per a recent Us Weekly) or bemoaning the length of his conquest list, he's apparently brokering peace between warring factions.

On Monday night at Manhattan hot spot Butter, the crooner worked his matchmaker magic by "playing relationship counselor" for mercurial ex-inamoratas Lindsay Lohan and Samantha Ronson, reports the New York Daily News.

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"Lindsay and Sam didn't arrive together," recounts a fellow reveler. "Lindsay walked in, and the two said a quick hello, but then Linds went to the table where John was sitting."

Ronson, who was deejaying at the club, made her way to the table a little later, but she apparently situated herself as far away from her sometime squeeze as possible.

"Lindsay looked upset that Sam hadn't come over to her, and she started whispering to John, who looked like he was trying to calm her down," extrapolates the spy. "She looked pretty angry. Then John got up and went to talk to Sam."

RELATED: See more pics of John Mayer

Silver-tongued devil that he thinks he is, Mayer had a short confab with Ronson that ended with her heading over to LiLo.

The squabble-disposed pair, who recently steered clear of each other while hanging out at a club in Los Angeles, ended up "talking and laughing."

"Lindsay seemed happier than she has in ages," says the eyewitness. "Sam eventually got up and deejayed for a while, and Lindsay kept standing up and looking over to the deejay booth, smiling."

The pair packed it in around 3 a.m., and although they exited separately, "They definitely ended the night on good terms," concludes the snitch.

The New York Post confirms Lohan's uncharacteristically placid state, with a spy relaying, "She was totally sober and well-behaved. She seemed like she was having fun."

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But not too much fun. Lindsay has already fired back at speculation that she appeared "very interested" in Mayer while whooping it up at the club.

"She would follow his every move," a snitch maintains to E! News. "He would dance with the waitresses and then come back. She was way into it."

Not so, insists Lindsay, who assures Gossip Cop that nothing untoward went on.

Speaking of untoward, the latest cover of Us Weekly accuses the drama-dependent starlet of hitting "a new low." The charge: She was supposedly "caught kissing" Jessica Alba's husband, Cash Warren. Expect Lohan's vehement denial in 3 ... 2 ...

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