What happened with Chris Brown and Rihanna?

L.A. cops are investigating what went wrong this weekend between RB singer Chris Brown and his pop superstar girlfriend, Rihanna. Police say that after Clive Davis pre-Grammy party, Brown and a woman who was later identified by multiple sources as Rihanna, drove through L.A.s ritzy Hancock Park about 12:30 a.m. Sunday in a rented Lamborghini and started arguing. After they got out of the car, the fight escalated. A witness called 911, but Brown had fled by the time officers arrived. Rihanna was treated at Los Angeles Cedars-Sinai Medical Center and released. Her publicist says shes ``well. Brown -- who just lost his Doublemint gum endorsement -- turned himself in while the Grammys went on without him ( Al Green stepped in for the duet with Justin Timberlake ). Released after posting $50,000 bail, he is due in court in March.