A former Olympian and longtime track coach has pleaded not guilty and been ordered held on $200,000 bail on charges that he sexually molested boys while working at a sports camp in western Massachusetts in the 1970s. Conrad Mainwaring, who was a hurdler for Antigua and Barbuda in the 1976 Summer Olympics in Montreal, was arraigned Tuesday in Berkshire Superior Court on nine counts of indecent assault and battery on a child over 14 and three counts of indecent assault and battery on a child under 14, according to a statement from the office of District Attorney Andrea Harrington. Mainwaring, a 69-year-old Los Angeles resident and United Kingdom national, molested campers from 1975 to 1979 while working as a counselor at Camp Greylock in Becket, prosecutors alleged.