Hibernate version: 2.1.6

Mapping documents:
<class name="User" table="T_FIN_USER">

<id name="userID" column="USER_ID" type="string" unsaved-value="null">
<generator class="assigned"/>
</id>

<set name="buUserRel" inverse="true" cascade="all-delete-orphan">
<key column="USER_ID"/>
<one-to-many class="BuUserRel"/>
</set>

<property name="password" column="PASSWORD" type="string"/>
<property name="name" column="NAME" type="string"/>
<property name="badgeNo" column="BADGE_NO" type="string"/>
<property name="financeInd" column="FINANCE_IND" type="string"/>

<!-- Apply to all object derrived from BaseBO -->
<property name="createdBy" column="CREATED_BY" type="string"/>
<property name="createdDt" column="CREATED_DT" type="timestamp"/>
<property name="lastModifiedBy" column="LAST_MODIFIED_BY" type="string"/>
<property name="lastModifiedDt" column="LAST_MODIFIED_DT" type="timestamp"/>

</class>

<class name="BuUserRel" table="T_FIN_BU_USER_REL">

<id name="id" column="ID" type="long" unsaved-value="null">
<generator class="increment"/>
</id>

<many-to-one name="bu" column="BU_NO" class="BU" not-null="true"/>

<many-to-one name="user" column="USER_ID" class="User" not-null="true"/>

<!-- Apply to all object derrived from BaseBO -->
<property name="createdBy" column="CREATED_BY" type="string"/>
<property name="createdDt" column="CREATED_DT" type="timestamp"/>
<property name="lastModifiedBy" column="LAST_MODIFIED_BY" type="string"/>
<property name="lastModifiedDt" column="LAST_MODIFIED_DT" type="timestamp"/>

</class>


Code between sessionFactory.openSession() and session.close():
session = getSession();
Transaction tx = session.beginTransaction();
User oldUser = (User)session.get(User.class, user.getUserID());
loop through created objects
oldUser.getBuUserRel().add(buUserRel);
endloop
loop through removed objects
oldUser.getBuUserRel().remove(oldBuUserRel);
endloop

If I don't have removed objects, then every thing is ok, the created objects are created in database. But when I reach the remove code, I have this:
Full stack trace of any exception that occurs:
net.sf.hibernate.HibernateException: net.sf.hibernate.ObjectDeletedException: deleted object would be re-saved by cascade (remove deleted object from associations): 9, of class: com.psca.M28000.bo.BuUserRel
at com.psca.M28000.dao.M28000_DAO.updateUser(M28000_DAO.java:424)
at com.psca.M28000.action.EditUserOnSubmitAction.execute(EditUserOnSubmitAction.java:67)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:421)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:226)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1164)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:417)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:768)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at com.evermind[Oracle Application Server Containers for J2EE 10g (9.0.4.0.0)].server.http.ResourceFilterChain.doFilter(ResourceFilterChain.java:65)
at oracle.security.jazn.oc4j.JAZNFilter.doFilter(Unknown Source)
at com.evermind[Oracle Application Server Containers for J2EE 10g (9.0.4.0.0)].server.http.ServletRequestDispatcher.invoke(ServletRequestDispatcher.java:604)
at com.evermind[Oracle Application Server Containers for J2EE 10g (9.0.4.0.0)].server.http.ServletRequestDispatcher.forwardInternal(ServletRequestDispatcher.java:317)
at com.evermind[Oracle Application Server Containers for J2EE 10g (9.0.4.0.0)].server.http.HttpRequestHandler.processRequest(HttpRequestHandler.java:790)
at com.evermind[Oracle Application Server Containers for J2EE 10g (9.0.4.0.0)].server.http.HttpRequestHandler.run(HttpRequestHandler.java:270)
at com.evermind[Oracle Application Server Containers for J2EE 10g (9.0.4.0.0)].server.http.HttpRequestHandler.run(HttpRequestHandler.java:112)
at com.evermind[Oracle Application Server Containers for J2EE 10g (9.0.4.0.0)].util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:192)
at java.lang.Thread.run(Thread.java:534)


Name and version of the database you are using: Oracle 9i

I don't know what is going on?

Any help is appreciated.

You're resaving and object by cascade, which have been deleted in the session. Be sure to update you association from a Java POV (esp bidirectional ones)