The following annotation produces an exception:

org.hibernate.MappingException:
Could not get constructor for org.hibernate.persister.collection.OneToManyPersister

org.hibernate.HibernateException:
Unable to parse order-by fragment

    @OneToMany  (mappedBy = "parent", fetch = FetchType.EAGER)
    @Fetch(FetchMode.SELECT)
    @org.hibernate.annotations.OrderBy(clause="CASE WHEN displayOrder is null then 1 else null end, displayOrder, category_name")
    public Set<Category> getSubcategories() {
        return subcategories;
    }

The error does not occur with Hibernate Annotations 3.4.0-GA.
All later versions I tried produce the error.