Hibernate SELECT queries causes unique constraint violation

I have a Hibernate SELECT query that keeps throwing a unique constraint violation - which seems odd given that I thought a constraint violation could only occur with an insert?

Probably significant - the unique constraint violation only occurs if I do it right after I do a save on the same DAO.

This is where a do a save for a DAO object:

this.llcPcdSchedDAO.create(newLlcPcdSched);

Which calls this in the BaseDAO object:

public <R> R create(R entity ){
    entityManager.persist( entity );
    return entity;
}

And this is my SELECT query and its code within the same DAO object - which then throws a unique constraint violation. As I said the constraint violation only occurs when I do the create first.

Query q = entityManager.createQuery("SELECT pcdSchedData FROM LlcPcdSchedData pcdSchedData WHERE pcdSchedData.profileVersion.profileVersionId = :selectId");
    q.setParameter("selectId", profileVersionId);
    try {
        List<LlcPcdSchedData> results = (List<LlcPcdSchedData>)(q.getResultList());
        LOG.debug("findByProfileVersionId(Long profileVersionId) successful, result size: " + results.size());
        return results;
    } catch (Exception e) {
        LOG.error("findByProfileVersionId(Long profileVersionId) failed", e);
        throw new MnsException(e);
    }

Thanks so much.