PREHEAT oven to 300° F. Grease 9-inch springform pan.
COMBINE crumbs and butter in medium bowl. Press onto bottom and 1 inch up side of prepared pan.
BEAT cream cheese and granulated sugar in large mixer bowl until smooth. Add sour cream, flour and vanilla extract; mix well. Add eggs; beat on low speed until combined.
MELT butterscotch morsels in medium, uncovered microwave-safe bowl on MEDIUM-HIGH (70%) power for 1 minute; STIR. Morsels may retain some of their shape. If necessary, microwave at additional 10- to 15-second intervals, stirring just until morsels are melted. Add 1 1/2 cups batter into melted butterscotch morsels; stir. Pour into crust. Repeat procedure with semi-sweet morsels. Carefully spoon over butterscotch layer. Melt white morsels in small, uncovered, microwave-safe bowl as stated above. Blend melted white morsels into remaining batter in mixer bowl. Carefully spoon over semi-sweet layer, covering completely.
BAKE for 1 hour 10 to 15 minutes or until center is almost set. Cool in pan on wire rack for 10 minutes. Run knife around edge of cheesecake. Let stand for 1 hour.
PLACE each flavor of morsels separately in three, small heavy-duty plastic bags. Microwave on HIGH (100%) power for 20 seconds, knead bags to mix. Microwave at additional 10- second intervals, kneading until smooth. Cut a small hole in corner of bag; squeeze to drizzle over cheesecake. Refrigerate for at least 3 hours or overnight. Remove side of pan.