The Obama administration appears to be having as much trouble as its predecessors in decrypting the secrets of how to retain its cybersecurity advisers. Monday’s resignation of Melissa Hathaway, who served as acting senior director for cyberspace for the National Security and Homeland Security Councils, has Washington insiders and tech industry observers buzzing about yet another roadblock in President Obama’s intention to revamp network protection policy. Hathaway, a Bush administration holdover, completed a two-month study of U.S. cybersecurity policy in April.