I don't know what is wrong with attribute type case, but
in second case you have to add column element as content of type element
Code:
<class name="geofolksonomia.struts.entidad.Etiquetado" table="etiquetado">
<composite-id name="id" class="geofolksonomia.struts.entidad.EtiquetadoId">
<key-many-to-one name="codEtiqueta">
<type name="geofolksonomia.struts.entidad.Etiqueta">
<column name="codEtiqueta" />
</type>
</key-many-to-one>
<key-many-to-one name="codPostIt">
<type name="geofolksonomia.struts.entidad.PostIt">
<column name="codPostIt"/>
</type>
</key-many-to-one>
</composite-id>
</class>