WASHINGTON (AP) - A Navy report predicts probable or likely failures in electrical and water systems for many cities because of the Year 2000 technology problem - an assessment more dire than any other made by the government. President Clinton's top Y2K adviser, John Koskinen, called the Navy's conclusions overly cautious, saying they assumed that major utilities would fail unless proved otherwise. The most recent version of the study, updated less than two weeks ago, predicted probable or likely partial failures in electric utilities that serve nearly 60 of roughly 400 Navy and Marine Corps facilities. The military report contrasts sharply with predictions from the White House, which weeks ago said in a report that national electrical failures are highly unlikely.