Place a greased 9-in. springform pan on a double thickness of heavy-duty foil (about 18 in. square). Securely wrap foil around pan. Combine the cracker crumbs, sugar and butter; press onto the bottom and 1-1/2 in. up sides of pan. Set aside.
In a large bowl, beat cream cheese and sugar until smooth. Beat in the sour cream, cornstarch and vanilla. Add eggs; beat on low speed just until combined. Spread into prepared pan.
In a food processor, combine ingredients for the squash layer. Gently spread over cheesecake layer. Place springform pan in a large baking pan; add 1 in. of hot water to larger pan.
Bake at 325° for 1-1/2 hours or until center is just set. Remove springform pan from water bath. Cool on a wire rack for 10 minutes. Carefully run a knife around edge of pan to loosen; cool 1 hour longer. Refrigerate overnight. Remove sides of pan. Yield: 16 servings.