Diddy-Diddling DenialKim Porter is in denial that Diddy is diddling Sienna Miller. (Also, his famous White Party is slated for September 2). Britney Spears was in a fender bender, after which she announced, “I’m a braniac!” On-again, off-again couple Marc Jacobs and Jason Preston are back on. Jeffrey Chodorow is keeping China Grill closed for a few extra days to get a new fridge and get rid of some insects. Phoenix Sun point guard Steve Nash got into a pickup soccer game at Central Park and scored two goals. The Freakanomics guys are moving their blog to the New York Times. Mort Zuckerman gets Harry Evan to help him write his weekly column in U.S. News. Chevy Chase found a $20 bill at a Hillary Clinton fund-raiser in the Hamptons. George Pataki is being considered for an ambassadorship.