anuary 11, 2005 -- EXCLUSIVE WASHINGTON — The criminal probe into why former Bill Clinton aide Sandy Berger illegally sneaked top-secret documents out of the National Archives — possibly in his socks — has heated up and is now before a federal grand jury, The Post has learned. The "Socks Docs" probe forced Berger, who was President Clinton's national security adviser, to step down as Democrat John Kerry's top foreign-policy adviser last summer. "It may have been off the front pages, but the investigation has been active," said a source with knowledge of the probe. "[Berger] has been interviewed several...