NonUniqueObjectException thrown when adding a new page in a plugin

b = new Page();
b.setTitle(source.getTitle());
b.setContent(source.getContent());
b.setSpace(spaceN);
b.setVersionComment(makePublishingComment(approvalCheck));
pageManager.saveContentEntity(b,new DefaultSaveContext());

2007-08-20 16:52:10,305 ERROR [http-8082-Processor3] [atlassian.xwork.interceptors.XWorkTransactionInterceptor] onThrowable Invoking 
rollback for transaction on action '/plugins/approvalsworkflow/save.action (ApprovalsAction.save())' due to throwable: 
org.springframework.orm.hibernate.HibernateSystemException: a different object with the same identifier value was already associated with
 the session: 17432578, of class: com.atlassian.confluence.spaces.Space; nested exception is net.sf.hibernate.NonUniqueObjectException: a
 different object with the same identifier value was already associated with the session: 17432578, of class:
 com.atlassian.confluence.spaces.Space
org.springframework.orm.hibernate.HibernateSystemException: a different object with the same identifier value was already associated with
 the session: 17432578, of class: com.atlassian.confluence.spaces.Space; nested exception is net.sf.hibernate.NonUniqueObjectException: a
 different object with the same identifier value was already associated with the session: 17432578, of class:
 com.atlassian.confluence.spaces.Space
net.sf.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: 
17432578, of class: com.atlassian.confluence.spaces.Space
        at net.sf.hibernate.impl.SessionImpl.checkUniqueness(SessionImpl.java:1687)
        at net.sf.hibernate.impl.SessionImpl.doUpdateMutable(SessionImpl.java:1453)
        at net.sf.hibernate.impl.SessionImpl.doUpdate(SessionImpl.java:1480)
        at net.sf.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:1403)
        at net.sf.hibernate.engine.Cascades$4.cascade(Cascades.java:114)
        at net.sf.hibernate.engine.Cascades.cascade(Cascades.java:436)
        at net.sf.hibernate.engine.Cascades.cascade(Cascades.java:503)
        at net.sf.hibernate.impl.SessionImpl.doSave(SessionImpl.java:901)
        at net.sf.hibernate.impl.SessionImpl.doSave(SessionImpl.java:868)
        at net.sf.hibernate.impl.SessionImpl.saveWithGeneratedIdentifier(SessionImpl.java:790)
        at net.sf.hibernate.impl.SessionImpl.save(SessionImpl.java:749)
        at net.sf.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:1398)
        at org.springframework.orm.hibernate.HibernateTemplate$16.doInHibernate(HibernateTemplate.java:532)
        at org.springframework.orm.hibernate.HibernateTemplate.execute(HibernateTemplate.java:312)
        at org.springframework.orm.hibernate.HibernateTemplate.saveOrUpdate(HibernateTemplate.java:529)
        at com.atlassian.hibernate.HibernateObjectDao.saveRaw(HibernateObjectDao.java:148)
        at com.atlassian.confluence.core.DefaultContentEntityManager.saveContentEntity(DefaultContentEntityManager.java:44)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:585)
        at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:284)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:155)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:122)
        at com.atlassian.spring.interceptors.SpringProfilingInterceptor.invoke(SpringProfilingInterceptor.java:20)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:144)
        at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:56)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:144)
        at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:174)
        at $Proxy19.saveContentEntity(Unknown Source)