"- Tom Bosh lowered the telephone receiver into its cradle, making a decision on the way down. ``We're not buying any more,'' he told his traders at Bank of New York Co. ``Nothing.'' It was May 2007, and Bosh, who managed $25 billion from the bank's 13th-floor trading room above Times Square, had just hung up on Ralph Cioffi at Bear Stearns Cos. a dozen blocks away. Bosh had invested $50 million in notes from an issuer Cioffi controlled, and he was ready to pull the plug. "