当对具有一对多关系的对象使用版本乐观锁定时，NHibernate StaleObjectStateException

I am using NHibernate and ASP.Net using a session per request as suggested in the best practices article by Billy McCafferty (sorry, I cannot include the link). I have used this successfully with version optimistic locking, saving updated objects in the HTTP Session object and reattaching to the NHibernate session using the SaveOrUpdate method.I am using NHibernate and ASP.Net using a sessi