CatalogClassTypes.AllClassTypesClass never returns all class types

Hi,

I want to retieve all products from a category including the products 
variants in a single dataset, however when I set the CatalogClassTypes to 
AllClassTypesClass the variants are not returned.

I have performed a trace on the stored procedure calls and the i_ClassType

property defaults to 12, however when I change this to 63 (All Class
Types) 
and execure in query analyser I get the variants included on the dataset.

Here's the code

CategoryConfiguration categoryConfiguration = new CategoryConfiguration();
    categoryConfiguration.LoadChildProducts = true;
    categoryConfiguration.ChildProducts.SearchOptions = new 
CatalogSearchOptions();
    categoryConfiguration.ChildProducts.SearchOptions.PropertiesToReturn =

Helpers.GetDefaultProductPropertiesToReturn();
    categoryConfiguration.ChildProducts.SqlWhereClause = 
Helpers.GetDefaultSqlWhereClause();
    categoryConfiguration.ChildProducts.SearchOptions.ClassTypes = 
CatalogClassTypes.AllClassTypesClass;
    categoryConfiguration.InventoryOptions = 
Helpers.GetDefaultInventoryOptions();

    try
    {
     //Attempt to get the Category's child products
     products = CatalogHelper.GetCatalog().GetCategory(categoryName, 
categoryConfiguration).ChildProducts.DataSet;
    }
    catch (Exception ex)
    {
     bool rethrow = ExceptionPolicy.HandleException(ex, 
"BasePlatformPolicy");

     if (rethrow)
      throw;
    }

Can anyone enlighten me as to why I cant get all class types out in a
single 
call.

Thanks

Nick