I just saw this on IMDB:
Best Achievement in EditingWinner: Slumdog Millionaire (2008) - Chris DickensBest Achievement in SoundWinner: Slumdog Millionaire (2008) - Ian Tapp, Richard Pryke, Resul PookuttyBest Achievement in Sound EditingWinner: The Dark Knight (2008) - Richard King
It seems to me that if you win for Best Sound, and win for Best Editing, you should also win for Best Sound Editing.