Hibernate - Constraint Violation

Cannot add or update a child row&58; a foreign key constraint fails (`classificado`.`categoria`, CONSTRAINT `FK5D54E133D5480FAC` FOREIGN KEY (`categoria_id`) REFERENCES `categoria` (`id`))

Hibernate&58; insert into categoria (categoria_id, descricao, nome) values (&63, &63, &63) //log do hibernate
05/02/2010 08&58;47&58;01 org.apache.catalina.core.StandardWrapperValve invoke
SEVERE&58; Servlet.service() for servlet struts threw exception
com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException&58; Cannot add or update a child row&58; a foreign key constraint fails (`classificado`.`categoria`, CONSTRAINT `FK5D54E133D5480FAC` FOREIGN KEY (`categoria_id`) REFERENCES `categoria` (`id`))
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java&58;39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java&58;27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java&58;513)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java&58;406)
    at com.mysql.jdbc.Util.getInstance(Util.java&58;381)

    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java&58;3491)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java&58;3423)
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java&58;1936)
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java&58;2060)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java&58;2542)
    //... continuação da exception.. nada de importante depois daqui

@Entity
@Table(name = "categoria")
public class Categoria implements Serializable {

    @Id @GeneratedValue
    @Column(name = "id")
    private Integer id;
    
    @Column(name = "nome", length = 80, nullable = false)
    private String nome;
   
    @Column(name = "descricao", length = 150, nullable=true)
    private String descricao;
   
        // A questão é que tanto nessa parte quanto no banco essa foreign key pode ser null (categoria_id)
        // essa categoria representa a categoria pai dessa categoria
    @ManyToOne
    @JoinColumn(name = "categoria_id", nullable=true)
    private Categoria categoriaPai;
   
    @OneToMany(mappedBy = "categoriaPai", fetch = FetchType.EAGER)
    @Fetch(FetchMode.SUBSELECT)
    private List subCategorias;


}