HibernateQueryException: Not supported for DML operations

Hi all, I got this strange exception

HibernateQueryException: Not supported for DML operations

            delete from com.avid.interplay.tags.TagAssignment
assignment
            where assignment.element = :element
            and assignment.tag = :tag

by executing a Hibernate query:

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
            delete from com.avid.interplay.tags.TagAssignment
assignment
            where assignment.element = :element
            and assignment.tag = :tag
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

Looks like DML clauses are not supported? But another piece similar
code runs fine.
I am using Hibernate 3 with a hsql server.

where TagAssignment looks like

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

public class TagAssignment {
    private Long id;
    private ElementProxy element;
    private Tag tag;

    protected TagAssignment() {
    }

    public TagAssignment(ElementProxy element, Tag category) {
        this.element = element;
        this.tag = category;
    }

    public ElementProxy getElement() {
        return element;
    }

    public Tag getTag() {
        return tag;
    }
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

This is my method call:

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
HibernateCallback callback = new HibernateCallback() {
            public Object doInHibernate(Session session) throws
HibernateException, SQLException {
                Query query =
session.getNamedQuery("com.avid.interplay.tags.TagAssignment.deleteFromProxy");
                query.setParameter("element", element);
                query.setParameter("tag", tag);
                return query.list();
            }
        };
        getHibernateTemplate().execute(callback);
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

Thanks a lot.