The downtown Manhattan apartment building where the late John F. Kennedy Jr. and Carolyn Bessette Kennedy lived is again the focus of attention. Just when it seemed that actor/director Ed Burns and his girlfriend, actress Heather Graham, would be settling into the Kennedys’ 2,400-square-foot loft, comes news that Burns lost his chance by allegedly ticking off the building’s co-op board by postponing meetings. Meanwhile, David Letterman, who already owns two apartments in the 12-unit building, had a tough time with the co-op board, too. The Davester, says the New York Post, had to face the board in February, while he was recuperating from his January heart bypass, in his attempt to buy a third apartment. The board said yes, but not until he groveled first, says the Post, which goes on to report that while Letterman spends most of his time at his house in New Canaan, Conn., his girlfriend, Regina Lasko, lives in the Manhattan space.