XWikiAttachment randomly and suddenly altered when attachment contain non ascii characters

I have an issue that occurs within the life of a xwiki page, I unfortunately don't know the scenario that lead to this xwiki exception showing up on the page

Wrapped Exception:

org.hibernate.HibernateException: identifier of an instance of com.xpn.xwiki.doc.XWikiAttachment altered from -423758546 to -1462378896
at org.hibernate.event.def.DefaultFlushEntityEventListener.checkId(DefaultFlushEntityEventListener.java:51)
at org.hibernate.event.def.DefaultFlushEntityEventListener.onFlushEntity(DefaultFlushEntityEventListener.java:82)
at org.hibernate.event.def.AbstractFlushingEventListener.flushEntities(AbstractFlushingEventListener.java:190)
at org.hibernate.event.def.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:70)
at org.hibernate.event.def.DefaultAutoFlushEventListener.onAutoFlush(DefaultAutoFlushEventListener.java:39)
at org.hibernate.impl.SessionImpl.autoFlushIfRequired(SessionImpl.java:707)
at org.hibernate.impl.SessionImpl.prepareQueries(SessionImpl.java:891)
at org.hibernate.impl.SessionImpl.getQueries(SessionImpl.java:881)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:830)
at org.hibernate.impl.QueryImpl.list(QueryImpl.java:74)

All I know is that I'm defintely not the only one:

http://www.google.com/search?client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial_s&hl=en&q=Wrapped+Exception%3A+identifier+of+an+instance+of+com.xpn.xwiki.doc.XWikiAttachment+altered&btnG=Google+Search

But what seems weird is that I didn't find it in your jira bugtracker.

the exception logged in catalina.out is

java.lang.NullPointerException
at com.xpn.xwiki.notify.XWikiNotificationManager.verify(XWikiNotificationManager.java:86)
at com.xpn.xwiki.web.ViewEditAction.execute(ViewEditAction.java:268)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:421)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:226)