Put popped corn in large bowl. Combine sugars, syrup, water, vinegar and salt in a 2 quart sauce pan. Heat to boiling over medium high heat, stirring frequently. Once it starts boiling stir constantly until small amount of mixture dropped into very cold water forms a ball (hard ball stage). Reduce heat to low and stir in butter until melted. Pour syrup over popcorn in bowl, stirring until well coated. Let cool slightly. Butter hands and shape into balls.