I need help with pillsbury holiday moments cookies?

I have tried numerous times over the years to make these cookies and have yet to succeed. The dough is dry and hard to shape and when finally putting them into the oven, they fall apart and spread. I follow this recipe to a 'T' and have no idea what I am doing wrong!!! Here is the recipe

1 cup butter or margarine, softened

3/4 cup cornstarch

1/3 cup powdered sugar

1 cup all-purpose flour

3 tablespoons powdered sugar

2 tablespoons red decorator sugar crystals

2 tablespoons green decorator sugar crystals

Directions

In large bowl, beat with electric mixer until light and fluffy. Add cornstarch and 1/3 cup powdered sugar; beat on low speed until moistened. Beat on high speed until light and fluffy. Add flour; mix until dough forms. Cover with plastic wrap; refrigerate at least 1 hour for easier handling.

Heat oven to 350 F. Shape dough into 1-inch balls; place 1 inch apart on the ungreased cookie sheets.

Bake 9 to 15 minutes or until cookies are very light golden brown. Cool 1 minute; remove from cookie sheets.

In small bowl, mix 3 tablespoons powdered sugar and both decorator sugars; carefully roll warm cookies in mixture.

HELP!!!