HELP!! I have baked 3 Sundrop pound cake in the last few weeks, for some reason the top 1/2" separates/cracks from the rest of the cake.  I have never had this problem with any of my other pound cakes.  Could the problem be caused from the carbonations in the Sundrop?

Usually too much sugar  - reduce it - maybe 1/2 cup?

From their web site - 

5 eggs 
3 cups sugar 
3 cups plain sifted flour 
2 sticks butter or margarine 
½ cup Shortening 
1 teaspoon vanilla flavoring 
1 teaspoon lemon flavoring 
6 ounces regular SUN DROP