Sunday, February 08, 2009 By Roger Friedman Whitney Houston is back. Last night she took the stage at Clive Davis’ annual pre-Grammy bash and wowed the crowd with a medley of hits. She was clean, sober, and joyous, absolutely radiant and healthy. Houston knew it was a triumph and she gained confidence as she went from her opening ballad—a shortened version of “I Will Always Love You” through a few of her hits ending with a buoyant “I’m Every Woman.” If there was a fear that her voice was gone, she dispelled it. And while she may not be singing the way she did at 25, the 45 year old is still among the very premiere song stylists in the world. And that’s saying a lot at Davis’s famous pre-Grammy show. Last night the featured perfomers before Houston took the stage included a magnificent Jennifer Hudson, Kelly Clarkson, Leona Lewis, as well as Rod Stewart, Barry Manilow, Josh Groban (substituting for Usher), rockers Kings of Leon, and Sean Puffy Combs featuring Faith Evans in the evening’