In a small saucepan combine the pineapple juice, sugar and ginger root. Bring to a boil, stir until sugar is dissolved.
Reduce heat. Simmer, uncovered, over medium heat for about 6 minutes until it has the consistency of a thin syrup.
Remove from heat and cool. Place in a bowl.
Add the melon balls and 2 cups of the cantaloupe balls. Cover and chill overnight.
Blend or process strawberries until smooth. Pour into a bowl and set aside.
Cover and blend or process the last 2 cups as of cantaloupe balls until smooth. In a large bowl mix the yogurt and sour cream.
Add strawberries, blended melon balls and milk. Stir well to combine smoothly.
Cover and chill overnight. When ready to serve, drain the melon balls, reserving the syrup.
Stir the syrup into the chilled soup. Ladle soup into bowls and top with melon balls. Serves 8 to 10.