Viewing a particular page generates exception

I created a page with a lot of attachments (42 pictures, you may count 45 in the page code but some are repeated). After editing the pag in the wysiwyg editor, clicking on the picture button, I got a message "401 : not authorized" and I lost the authentication with the stack trace below.

The bug is hard to reproduce, but once it's there, the only way to avoid loosing authentication is to delete the XWiki.lskywalk page (lskywalk is the author, the creator and the viewer of the page). Flushing the cache, restarting the server, even physically reboot the machine... Won't work either.

The attached wiki code seems to cause the problem, especially whitout the pictures. Tha same code still causes a problem if it is copy-pasted on a different page.

Here is the attached log: it's warn mode, I saved the 41 MB debug mode log but I won't upload it unless it's really needed.
---------------------------------------------------------------------
2008-04-01 17:08:29,446 http://anakin:8080/xwiki/bin/view/Main/WebHome [http-8080-1] INFO .AbstractXWikiMigrationManager - No storage migration required since current version is [7351]
2008-04-01 17:08:55,739 http://anakin:8080/xwiki/bin/download/Utilisation/FenetreCartographique/selectionMenu.png [http-8080-11] WARN LDAP.XWikiLDAPAuthServiceImpl - LDAP authentication failed.
com.xpn.xwiki.XWikiException: Error number 3201 in 3: Exception while saving document XWiki.lskywalk
Wrapped Exception: Error number 3212 in 3: Exception while saving property tags of object XWiki.lskywalk
Wrapped Exception: Illegal attempt to associate a collection with two open sessions
at com.xpn.xwiki.store.XWikiHibernateStore.saveXWikiDoc(XWikiHibernateStore.java:457)
at com.xpn.xwiki.store.XWikiCacheStore.saveXWikiDoc(XWikiCacheStore.java:97)
at com.xpn.xwiki.store.XWikiCacheStore.saveXWikiDoc(XWikiCacheStore.java:91)
at com.xpn.xwiki.XWiki.saveDocument(XWiki.java:1078)
at com.xpn.xwiki.XWiki.saveDocument(XWiki.java:1051)
at com.xpn.xwiki.XWiki.saveDocument(XWiki.java:1045)
at com.xpn.xwiki.user.impl.LDAP.XWikiLDAPAuthServiceImpl.updateUserFromLDAP(XWikiLDAPAuthServiceImpl.java:725)
at com.xpn.xwiki.user.impl.LDAP.XWikiLDAPAuthServiceImpl.syncUser(XWikiLDAPAuthServiceImpl.java:417)
at com.xpn.xwiki.user.impl.LDAP.XWikiLDAPAuthServiceImpl.ldapAuthenticate(XWikiLDAPAuthServiceImpl.java:297)
at com.xpn.xwiki.user.impl.LDAP.XWikiLDAPAuthServiceImpl.authenticate(XWikiLDAPAuthServiceImpl.java:107)
at com.xpn.xwiki.user.impl.xwiki.MyFormAuthenticator.authenticate(MyFormAuthenticator.java:194)
at com.xpn.xwiki.user.impl.xwiki.MyFormAuthenticator.processLogin(MyFormAuthenticator.java:95)
at com.xpn.xwiki.user.impl.xwiki.XWikiAuthServiceImpl.checkAuth(XWikiAuthServiceImpl.java:214)
at com.xpn.xwiki.XWiki.checkAuth(XWiki.java:3258)
at com.xpn.xwiki.user.impl.xwiki.XWikiRightServiceImpl.checkAccess(XWikiRightServiceImpl.java:166)
at com.xpn.xwiki.XWiki.checkAccess(XWiki.java:3266)
at com.xpn.xwiki.XWiki.prepareDocuments(XWiki.java:4210)
at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:164)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at com.xpn.xwiki.web.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:117)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:263)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:584)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:619)

Wrapped Exception:

com.xpn.xwiki.XWikiException: Error number 3212 in 3: Exception while saving property tags of object XWiki.lskywalk
Wrapped Exception: Illegal attempt to associate a collection with two open sessions
at com.xpn.xwiki.store.XWikiHibernateStore.saveXWikiProperty(XWikiHibernateStore.java:1151)
at com.xpn.xwiki.store.XWikiHibernateStore.saveXWikiCollection(XWikiHibernateStore.java:776)
at com.xpn.xwiki.store.XWikiHibernateStore.saveXWikiDoc(XWikiHibernateStore.java:436)
at com.xpn.xwiki.store.XWikiCacheStore.saveXWikiDoc(XWikiCacheStore.java:97)
at com.xpn.xwiki.store.XWikiCacheStore.saveXWikiDoc(XWikiCacheStore.java:91)
at com.xpn.xwiki.XWiki.saveDocument(XWiki.java:1078)
at com.xpn.xwiki.XWiki.saveDocument(XWiki.java:1051)
at com.xpn.xwiki.XWiki.saveDocument(XWiki.java:1045)
at com.xpn.xwiki.user.impl.LDAP.XWikiLDAPAuthServiceImpl.updateUserFromLDAP(XWikiLDAPAuthServiceImpl.java:725)
at com.xpn.xwiki.user.impl.LDAP.XWikiLDAPAuthServiceImpl.syncUser(XWikiLDAPAuthServiceImpl.java:417)
at com.xpn.xwiki.user.impl.LDAP.XWikiLDAPAuthServiceImpl.ldapAuthenticate(XWikiLDAPAuthServiceImpl.java:297)
at com.xpn.xwiki.user.impl.LDAP.XWikiLDAPAuthServiceImpl.authenticate(XWikiLDAPAuthServiceImpl.java:107)
at com.xpn.xwiki.user.impl.xwiki.MyFormAuthenticator.authenticate(MyFormAuthenticator.java:194)
at com.xpn.xwiki.user.impl.xwiki.MyFormAuthenticator.processLogin(MyFormAuthenticator.java:95)
at com.xpn.xwiki.user.impl.xwiki.XWikiAuthServiceImpl.checkAuth(XWikiAuthServiceImpl.java:214)
at com.xpn.xwiki.XWiki.checkAuth(XWiki.java:3258)
at com.xpn.xwiki.user.impl.xwiki.XWikiRightServiceImpl.checkAccess(XWikiRightServiceImpl.java:166)
at com.xpn.xwiki.XWiki.checkAccess(XWiki.java:3266)
at com.xpn.xwiki.XWiki.prepareDocuments(XWiki.java:4210)
at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:164)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at com.xpn.xwiki.web.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:117)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:263)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:584)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:619)

Wrapped Exception:

org.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions
at org.hibernate.collection.AbstractPersistentCollection.setCurrentSession(AbstractPersistentCollection.java:410)
at org.hibernate.event.def.OnUpdateVisitor.processCollection(OnUpdateVisitor.java:43)
at org.hibernate.event.def.AbstractVisitor.processValue(AbstractVisitor.java:101)
at org.hibernate.event.def.AbstractVisitor.processValue(AbstractVisitor.java:61)
at org.hibernate.event.def.AbstractVisitor.processEntityPropertyValues(AbstractVisitor.java:55)
at org.hibernate.event.def.AbstractVisitor.process(AbstractVisitor.java:123)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.performUpdate(DefaultSaveOrUpdateEventListener.java:293)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsDetached(DefaultSaveOrUpdateEventListener.java:223)
at org.hibernate.event.def.DefaultUpdateEventListener.performSaveOrUpdate(DefaultUpdateEventListener.java:33)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:70)
at org.hibernate.impl.SessionImpl.fireUpdate(SessionImpl.java:564)
at org.hibernate.impl.SessionImpl.update(SessionImpl.java:552)
at org.hibernate.impl.SessionImpl.update(SessionImpl.java:544)
at com.xpn.xwiki.store.XWikiHibernateStore.saveXWikiProperty(XWikiHibernateStore.java:1082)
at com.xpn.xwiki.store.XWikiHibernateStore.saveXWikiCollection(XWikiHibernateStore.java:776)
at com.xpn.xwiki.store.XWikiHibernateStore.saveXWikiDoc(XWikiHibernateStore.java:436)
at com.xpn.xwiki.store.XWikiCacheStore.saveXWikiDoc(XWikiCacheStore.java:97)
at com.xpn.xwiki.store.XWikiCacheStore.saveXWikiDoc(XWikiCacheStore.java:91)
at com.xpn.xwiki.XWiki.saveDocument(XWiki.java:1078)
at com.xpn.xwiki.XWiki.saveDocument(XWiki.java:1051)
at com.xpn.xwiki.XWiki.saveDocument(XWiki.java:1045)
at com.xpn.xwiki.user.impl.LDAP.XWikiLDAPAuthServiceImpl.updateUserFromLDAP(XWikiLDAPAuthServiceImpl.java:725)
at com.xpn.xwiki.user.impl.LDAP.XWikiLDAPAuthServiceImpl.syncUser(XWikiLDAPAuthServiceImpl.java:417)
at com.xpn.xwiki.user.impl.LDAP.XWikiLDAPAuthServiceImpl.ldapAuthenticate(XWikiLDAPAuthServiceImpl.java:297)
at com.xpn.xwiki.user.impl.LDAP.XWikiLDAPAuthServiceImpl.authenticate(XWikiLDAPAuthServiceImpl.java:107)
at com.xpn.xwiki.user.impl.xwiki.MyFormAuthenticator.authenticate(MyFormAuthenticator.java:194)
at com.xpn.xwiki.user.impl.xwiki.MyFormAuthenticator.processLogin(MyFormAuthenticator.java:95)
at com.xpn.xwiki.user.impl.xwiki.XWikiAuthServiceImpl.checkAuth(XWikiAuthServiceImpl.java:214)
at com.xpn.xwiki.XWiki.checkAuth(XWiki.java:3258)
at com.xpn.xwiki.user.impl.xwiki.XWikiRightServiceImpl.checkAccess(XWikiRightServiceImpl.java:166)
at com.xpn.xwiki.XWiki.checkAccess(XWiki.java:3266)
at com.xpn.xwiki.XWiki.prepareDocuments(XWiki.java:4210)
at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:164)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at com.xpn.xwiki.web.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:117)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:263)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:584)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:619)

... And the whole thing (LDAP warning, exceptions) is repeated 42 times, which is the number of different pictures in the page.

Thanks in advance !