crosstab function

postgres 8.2.17

I am trying out the crosstab function (tablefunc contrib) for reporting
needs and I'm having a problem.
I have customers and products and the data is the quantity purchased. I
am grouping by customername, productname in the source sql. My category
sql depends if I want the products or customers to be the columns.

When I make customers the rows and products the columns, it works fine.
But when I make customers the columns and products the rows, there are
duplicate product rows.

Is there a way to group the product rows so that the data results come
back correct?