04/21/2004 at 01:00 AM EDT
Whitney Houston received two standing ovations at last night's Arista Records 25th anniversary bash in Los Angeles. The star, whose erratic behavior of late included having to bow out of singing at the Oscars, sang a 20-minute, six-song medley. The show, which honored the record label's founder Clive Davis -- who signed Houston to the label when she was a teen -- will air as a two-hour NBC special on May 15. "The record's not over yet, remember," Houston, 36, mysteriously told the crowd. "God bless you. I love you." After the performance, Clive Davis told PEOPLE, "She proved tonight she still can soar." As for the rumors of a drug problem that have circulated around his star, Davis said, "I'm not going to talk about personal things." Backstage, Houston's cousin Dionne Warwick denied a report in this week's PEOPLE that she and Natalie Cole were going to approach Houston to discuss substance abuse. Asked by PEOPLE whether or not she advises Houston at all, Warwick said, "I support her. I care for her, but no, I don't advise her."