Butter a 9 inch square pan. To prepare crust, combine crumbs, sugar and margarine in a mixing bowl. Press mixture firmly into prepared pan. Chill 1 hour or until firm. Or bake in a 375 degree F (190 degrees C) oven for 10 minutes or until edges are brown. Cool on rack before filling.
To prepare filling, combine ice cream, pumpkin, brown sugar, ginger, cinnamon, nutmeg, and orange juice, and pour into crust. Freeze until ready to serve. Remove from freezer 15 minutes before serving, then cut into squares.
NOTES: I have also made the crust with crushed gingersnaps or vanilla wafers instead of graham cracker crumbs - both were good.