SYDNEY, AUSTRALIA  [Wednesday May.23.2007]  /Mix103FM.com/ -- Nicole Richie and her latest beau, Good Charlotte singer Joel Madden, have called it a day.

Sources says the pair split after a recent trip to Australia for the MTV Music Awards. According to Sydney's Daily Telegraph, "Joel was acting like a single man at the awards after party and the couple openly argued in front of the crowd."

"Nicole was in tears at one stage, but no one really knows why."

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