I know this may sound too simple but I had the same problem and through trial and error found that it had to do with how tight/loose my quick releases were. If they were just a little bit too loose, I got the creak. Just for reference, the wheels in question are Ksyrium Elites.
Good Luck.
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Fredo, you're my older brother and I love you...but don't ever take sides, with anyone, against the family again...ever.