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The third time didn't prove the charm for Uma Thurman. The twice-married actress, 39, has called it quits with her Swiss financier fiancé, Arpad "Arki" Busson, 46, who slipped an 8-plus-carat rock on her finger in June of 2008.

The parting of ways apparently happened nearly two months ago, but "they remain friends," an insider assures

Details of the bust-up remain sketchy.

According to gossip maven Cindy Adams, who first reported the split, the couple allegedly had a "spat" (seems moneybags Busson may be suffering some financial setbacks courtesy of Bernie Madoff, while Thurman may be looking to focus on her career) and she "walked out in a huff."

You know, let's just have the oh-so-poetic Cindy take it from here: "There was no serious intent to break up, but it made the other side think this engagement should maybe be broken off. So she drew first blood, but it was only a nick. He killed it off, and the waltz has ended."

As for the knuckle-crushing ring, "She will probably give it back," a source tells People magazine. "She wants to return everything that is his."

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The twosome began dating in the summer of 2007 after meeting at an exclusive shindig in Milan. Both had gone through high-profile breakups: Uma divorced Ethan Hawke in 2004 (they have a son and a daughter), while Arki split from Elle Macpherson in 2005 (they have two sons).

Before meeting the London-based Busson, the ethereal star had sworn off marriage (her first union, to Gary Oldman, went belly-up in 1992).

"I'm going to have to retract my statement of never," she happily confessed to the London Sunday Times shortly after the behemoth-jeweled question-popping. "I'll have to eat my words -- what a surprise."

But Thurman, who called it quits with hotelier Andre Balazs a few months before she began dating Busson, has been taking her time getting down the aisle again.

"I'm happily engaged, but we haven't set a wedding up," she told the October issue of W. "I'm not in a rush to do anything. One day we'll do it, when we're ready."

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What Uma is ready for: broadening her big-screen horizons.

"I am a mother, but I need to do what I'm good at doing," she explained. "Even your kids need you to be who you are. I've been living at home [in New York] for work for a long time. If I don't leave soon, I'm going to literally choke my career to death."

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