Stir together sugar, soy sauce, ketchup, sherry, and salt in a bowl until sugar is dissolved, Pour marinade into a roasting pan, then add garlic and ginger, and ribs turning ribs to coat with marinade.
Marinate, covered and chilled, turning occasionally, at least 3 hours.
Preheat oven to 325 degrees
Line bottom of broiler pan with foil, then arrange ribs, rounded sides up on broiler rack, reserving marinade for basting ( discard garlic and ginger).
Roast in middle of oven, basting with marinade every 20 minutes ( do not baste during the last 10 minutes of cooking ), until ribs are tender and glaze is well browned, about 1 3/4 hours.
Discard any unused marinade. Let racks stand5 minutes, then cut into individuals ribs.