Britney Spears Raids Hollywood

Britney Spears made a rare social appearance Saturday night at Phil Maloof's birthday party at Drai's Hollywood.

Britney arrived around 9 p.m. with a handsome, dark-haired guy who was NOT her on-again-off-again boyfriend and former agent Jason Trawick. She spent most of the time on a couch chatting with Maloof, a longtime friend and part owner of Palms Casino in Vegas.

The identity of the gentleman who was with her is unknown but he may have been a bodyguard.

"She stayed for about an hour and had fun," says a party source, who didn't witness anything romantic between Britney and her mystery male. "She didn't mention Jason."

Also at the party (but arriving separately): her father, Jamie.

The VIP bash, held in Victor Drai's private lounge on the first floor, was sponsored by Maloof's new Black Star Beer, but our sources say Britney didn't have any.

"She was mellow but in a good mood," says a source. "She never would drink in front of her dad."