My database is being driven by my NHibernate mapping files.

I have a Category class that looks like the following :

public class Category {

        public Category() : this("") { }

        public Category(string name) {
            Name = name;
            SubCategories = new List<Category>();
            Products = new HashSet<Product>();
        }


        public virtual int ID { get; set; }
        public virtual string Name { get; set; }
        public virtual string Description { get; set; }
        public virtual Category Parent { get; set; }
        public virtual bool IsDefault { get; set; }
        public virtual ICollection<Category> SubCategories { get; set; }
        public virtual ICollection<Product> Products { get; set; }   

and here is my Mapping file :

<property name="Name" column="Name" type="string" not-null="true"/>
<property name="IsDefault" column="IsDefault" type="boolean" not-null="true" />
<property name="Description" column="Description" type="string" not-null="true" />

<many-to-one name="Parent" column="ParentID"></many-to-one>

<bag name="SubCategories" inverse="true">
  <key column="ParentID"></key>
  <one-to-many class="Category"/>
</bag>
<set name="Products" table="Categories_Products">
  <key column="CategoryId"></key>
  <many-to-many column="ProductId" class="Product"></many-to-many>
</set>

when I try to create the database I get the following error :

failed: The INSERT statement conflicted with the FOREIGN KEY SAME TABLE constraint "FK9AD976763BF05E2A". The conflict occurred in database "CoderForTraders", table "dbo.Categories", column 'CategoryId'. The statement has been terminated.

I looked on the net for some answers but found none. Thanks for your help