I suggest you to create an account in http://forum.hibernate.org, surf the forum and in case you couldn't find the solution for your bug, ask your problem out there. I am sure you will find a more precise answer from hibernate  team.
Meanwhile please consider that there are useful considerations that you shall follow to ask a question in hibernate forum, if you expose your hibernate jar version, jdbc-driver-version.jar, application server name and version, hbm files, cfg.xml (or in case of a mixture with spring ,hibernate.properties & related beans) along with conditions that made you to face the problem, they will answer you.
It's a better approach as it's faster and you face other people's problems, styles and technics.