SYDNEY, AUSTRALIA  [Wednesday May.23.2007]  /WMQT.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."

Wanna own a piece of Good Charlotte?

More on Good Charlotte