Justin Timberlake and Cameron Diaz, who announced last week that they’d split up, got into a heated argument at Prince’s Golden Globes afterparty early Tuesday morning.

The exes, who’d chatted politely during the awards ceremony and even shared laughs at InStyle’s annual afterparty, hit the rough patch in their officially amicable breakup at a wee-hours bash hosted by the singer at the Beverly Wilshire hotel.

According to witnesses, Timberlake was chatting with actress Jessica Biel when Diaz approached. Biel stepped away, and the former couple had a serious exchange.

Diaz walked away, Timberlake followed, and the two were soon spotted engaged in an intense 40-minute face-off in a side room.

Diaz reemerged looking composed, but not before Timberlake held his head in his hands and, says a witness, “slammed his fist (down) into a cabinet.”

The NY Post also reported the same fight,

CAMERON Diaz is not over Justin Timberlake just yet, and things got heated when she saw her ex chatting up Jessica Biel in L.A. after the Golden Globes. Sources say the temperamental star “blew up” at Biel after she saw Timberlake flirting with her. Diaz followed Timberlake to the In Style party at the Hilton Oasis, where “they had an awkward conversation.” The “Charlie’s Angels” star then trailed Timberlake to the Beverly Hilton rooftop for the Universal party, where she found him chatting up Biel – and screamed at the “Illusionist” star. “If that’s how she wants to get him back, it won’t work,” said our insider. “She’s desperate.” Reps for Diaz did not return our call.

I can’t imagine it’s easy to break up with someone after 4 years…I feel bad for both of them.