A tipster emailed us saying, "There's some sort of insanity from Fairway to the 72nd St subway station. Cops everywhere, streets closed off, flashing lights and no cars are budging - any idea what's going on?" Our stab in the dark: Possible motorcade for President Obama, who landed at JFK Airport this morning to attend the memorial for CBS anchor Walter Cronkite. The memorial is being held at Lincoln Center's Avery Fisher Hall and the expected guests include astronaut Buzz Aldrin, CBS News' Katie Couric, Andy Rooney and Bob Schieffer, and NBC News' Tom Brokaw, with musicians Jimmy Buffett, Michael Feinstein, Wynton Marsalis and the U.S. Marine Band.