LOS ANGELES, CA  [Thursday Jan.18.2007]  /WMQT.com/ -- Justin's and Cameron's friendly break-up has hit a bump in the road.

According to sources at People magazine, the ex-couple began arguing at Prince's Golden Globes afterparty. While they were all smiles during the ceremony and at the InStyle afterparty, things got a little heated later on, when Diaz approached Timberlake while he was talking to actress Jessica Biel.

Witnesses said that Biel walked away, leaving Justin and Cameron alone to argue for 40 minutes in a side room.

When they emerged from the room, Timberlake reportedly
"slammed his fist into a cabinet".

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