1. Preheat grill to medium-high heat.
2. To prepare salad, place potatoes in a large saucepan; cover with water. Bring to a boil. Reduce heat, and simmer 18 minutes or until tender. Drain; cut potatoes into quarters, and place in a large bowl. Set aside.
3. Lightly coat squash with cooking spray. Sprinkle evenly with 1/4 teaspoon salt and 1/8 teaspoon pepper. Place squash on grill rack; grill 2 minutes on each side or until browned and tender. Remove squash from heat, and add to potatoes.
4. To prepare dressing, combine chives and remaining ingredients in a small bowl; stir with a whisk. Pour dressing over potato mixture, tossing gently to combine. Serve salad warm or chilled.