R&B legend Whitney Houston passed away Saturday night at a room in the Beverly Hilton Hotel, casting a somber shadow over the Grammy Awards, held the following night at the Staples Center in LA.  An official cause of death may not be known for weeks, however, as the singer's autopsy results are being released at the request of police.  Houston was found in a bathtub by a member of her entourage, and police say there were no obvious signs of foul play, but police want the toxicology reports back before making an official determination on cause of death, which could be several weeks.