Paul Nassif in Beverly Hills, CA on July 31, 2012. Credit:

The ring is off!

One day after filing for legal separation from wife Adrienne Maloof, Real Housewives of Beverly Hills' Paul Nassif was spotted out and about yukking it up with pals with one accessory conspicuously absent: His wedding ring.

Plastic surgeon Nassif's July 30 filing came the same day the Bravo reality series was due to wrap its third season. In his petition for legal separation, Nassif, 50, asked for joint custody of the couple's sons, Gavin, 9, and 6-year-old twins Colin and Christian.

Married nine years, Nassif and Maloof, 50, simply "grew apart," a source tells the new issue of Us Weekly, out Friday.

"It's not a vindictive 'I hate you' situation," confirms an insider of the couple's relationship woes, which will play out on the new season of RHOBH.

Still, the Palms heiress -- worth an estimated $300 million -- and Nassif, who have a prenup, aren't ready to divorce just yet. "They are getting professional help and trying to save their marriage," says a second source. "But their relationship is very volatile. They are trying to do what's best for their kids."