Lock NPE after a fresh install when clicking the first time on a "Add New Page" action menu + engine

I just made a fresh installation of Jahia by installing the new default web template. Site in FR. I just accessed to the home page logued as root (default user after installation).

When clicking on my first action menu (add a new page) and having launch my first edition engine, I got this NPE:

[GC 168611K->71725K(1038784K), 0.0059847 secs]
[GC 170413K->72063K(1039104K), 0.0072001 secs]
2008-12-16 14:19:42,734: INFO [org.jahia.services.content.automation.RulesListener] - Executing rules for [/web/ContentPage_1, /web/ContentPage_1/basicLinkHeader, /web/ContentPage_1/navLink] ... and 9 other nodes
2008-12-16 14:19:42,953: INFO [org.jahia.services.content.automation.RulesListener] - Rules executed for [/web/ContentPage_1, /web/ContentPage_1/basicLinkHeader, /web/ContentPage_1/navLink] ... and 9 other nodes
2008-12-16 14:19:43,328: INFO [org.jahia.bin.Jahia] - Processed [/cms] user=[root] ip=[127.0.0.1] in [7172ms]
2008-12-16 14:19:47,125: WARN [org.jahia.resourcebundle.JahiaResourceBundle] - Resource [toolbar.itemgroups.monitoring] not found in class java.util.PropertyResourceBundle using locale [fr]
2008-12-16 14:19:47,125: WARN [org.jahia.resourcebundle.JahiaResourceBundle] - Resource [toolbar.itemgroups.monitoring] not found in class java.util.PropertyResourceBundle using locale [fr]
2008-12-16 14:19:47,140: WARN [org.jahia.resourcebundle.JahiaResourceBundle] - Resource [toolbar.itemgroups.page] not found in class java.util.PropertyResourceBundle using locale [fr]
2008-12-16 14:19:47,140: WARN [org.jahia.resourcebundle.JahiaResourceBundle] - Resource [toolbar.itemgroups.page] not found in class java.util.PropertyResourceBundle using locale [fr]
2008-12-16 14:19:47,281: INFO [org.jahia.services.content.automation.RulesListener] - Executing rules for [/content/users/root/private/j:applyAcl, /content/users/root/private/imports, /content/users/root/preferences/j:applyAcl] ... and 4 other nodes
2008-12-16 14:19:47,343: INFO [org.jahia.services.content.automation.RulesListener] - Set acl by property
2008-12-16 14:19:47,359: INFO [org.jahia.services.content.automation.RulesListener] - Set acl by property
2008-12-16 14:19:47,359: INFO [org.jahia.services.content.automation.RulesListener] - Set acl by property
2008-12-16 14:19:47,421: INFO [org.jahia.services.content.automation.RulesListener] - Rules executed for [/content/users/root/private/j:applyAcl, /content/users/root/private/imports, /content/users/root/preferences/j:applyAcl] ... and 4 other nodes
2008-12-16 14:19:47,718: INFO [org.apache.jackrabbit.core.persistence.bundle.util.LRUNodeIdCache] - num=561/10240 hits=9329 miss=671
2008-12-16 14:19:47,718: INFO [org.apache.jackrabbit.core.persistence.bundle.util.LRUNodeIdCache] - num=577/10240 hits=9419 miss=581
[GC 170751K->74672K(1039808K), 0.0242703 secs]
2008-12-16 14:19:59,250: ERROR [org.jahia.bin.errors.ErrorLoggingFilter] - java.lang.NullPointerException
java.lang.NullPointerException
at org.jahia.ajax.engines.ReleaseLockContainer.execute(ReleaseLockContainer.java:75)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
at org.jahia.bin.JahiaRequestProcessor.process(JahiaRequestProcessor.java:82)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.jahia.bin.filters.jcr.JcrSessionFilter.doFilter(JcrSessionFilter.java:23)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.tuckey.web.filters.urlrewrite.RuleChain.handleRewrite(RuleChain.java:164)
at org.tuckey.web.filters.urlrewrite.RuleChain.doRules(RuleChain.java:141)
at org.tuckey.web.filters.urlrewrite.UrlRewriter.processRequest(UrlRewriter.java:90)
at org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:417)
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:191)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:433)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:568)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:619)
2008-12-16 14:19:59,828: INFO [org.jahia.services.search.lucene.fs.JahiaIndexSearcher] - Opening Searcher@527035 main
2008-12-16 14:19:59,828: INFO [org.jahia.services.search.lucene.fs.JahiaIndexSearcher] - autowarming org.jahia.services.search.lucene.fs.JahiaIndexSearcher@527035 from org.jahia.services.search.lucene.fs.JahiaIndexSearcher@1e418
FilterCache

{cumulative_inserts=0, hits=0, cumulative_evictions=0, inserts=0, cumulative_lookups=0, lookups=0, cumulative_hitratio=0.00, cumulative_hits=0, hitratio=0.00, evictions=0, size=0}
2008-12-16 14:19:59,828: INFO [org.jahia.services.search.lucene.AbstractLuceneSearchIndexer] - Finished processing 2 indexing orders in 313ms.
2008-12-16 14:19:59,828: INFO [org.jahia.services.search.lucene.fs.JahiaIndexSearcher] - autowarming result for org.jahia.services.search.lucene.fs.JahiaIndexSearcher@527035
FilterCache{cumulative_inserts=0, hits=0, cumulative_evictions=0, inserts=0, cumulative_lookups=0, lookups=0, cumulative_hitratio=0.00, cumulative_hits=0, hitratio=0.00, evictions=0, size=0}

2008-12-16 14:19:59,828: INFO [org.jahia.services.search.lucene.fs.LuceneCoreSearcher] - Registered new searcher org.jahia.services.search.lucene.fs.JahiaIndexSearcher@527035
[GC 174896K->75051K(1040000K), 0.0237008 secs]