Place chicken in baking dish.
Combine white grape juice, lemon juice, ginger, garlic, salt and pepper in bowl.
Pour over chicken, cover with plastic wrap and refrigerate for about four hours.
Preheat grill or grill pan over medium high heat. Remove chicken from marinade; set marinade aside. Grill chicken thoroughly on both sides, until firm to the touch.
Remove to serving plate, cover and set aside.
Pour reserved marinade into medium-sized saucepan. Cook over high heat until marinade is syrupy and reduced to about 3/4 c.
Remove from heat and whisk in butter one piece at a time. Pour glaze over chicken and serve.