A federal judge was kept in the dark about failures in a computer system created to help track royalty payments that were owed to Native Americans, a court-appointed investigator reported yesterday. Last September, U.S. District Judge Royce C. Lamberth said Interior Secretary Gale A. Norton had defrauded the court by making misleading statements about the department's efforts to fix management problems of oil, gas, mining, timber and other royalties from Indian lands. That included covering up failures of the Trust Asset and Accounting Management System.