Drain crabmeat; press crabmeat between paper towels to remove excess moisture. Combine crabmeat, 2 tablespoons breadcrumbs, sour cream, and next 4 ingredients in a medium bowl; shape mixture into 4 patties. Dredge patties in remaining 1/4 cup breadcrumbs.
Coat a nonstick skillet with cooking spray; add margarine. Place over medium heat until margarine melts. Add patties, and cook 3 to 4 minutes on each side or until golden. Serve with Plum Sauce.