Thanks Marius, for replying, much appreciated. Find the screenshot here https://dl.dropboxusercontent.com/u/53941840/Screen%20Shot%202015-03-05%20at... Yes, the Upgrade button is there, but clicking it brought me there (the error message was not there initially and the wizard had asked me which version I'm upgrading from. I answered 6.4.1). And clicking it again makes the screen busy for a few minutes and returns to the same screen. It seems to be stuck in this loop. I found out that in Chrome I can hit Later and it lets me through to the Wiki, until the next login. And this screen takes it time, so quite annoying. Well at least it is a workaround. The logs show iMar 05, 2015 8:05:30 AM org.apache.catalina.startup.HostConfig deployDirectory INFO: Deploying web application directory /var/lib/tomcat7/webapps/Wiki 2015-03-05 08:05:43,010 [pool-2-thread-1] WARN o.x.e.i.ServletEnvironment - No permanent directory configured. Using temporary director y [/var/cache/tomcat7/Catalina/localhost/Wiki]. 2015-03-05 08:05:48,892 [pool-2-thread-1] WARN ltInstalledExtensionRepository - Invalid extension [org.xwiki.enterprise:xwiki-enterprise-ui -common-6.4.1] on namespace [wiki:xwiki] (InvalidExtensionException: Dependency [org.xwiki.platform:xwiki-platform-oldcore-[6.4.1]] is incom patible with the core extension [org.xwiki.platform:xwiki-platform-legacy-oldcore-6.4.2]) 2015-03-05 08:05:48,896 [pool-2-thread-1] WARN ltInstalledExtensionRepository - Invalid extension [org.xwiki.enterprise:xwiki-enterprise-ui -mainwiki-6.4.1] on namespace [wiki:xwiki] (InvalidExtensionException: Dependency [org.xwiki.platform:xwiki-platform-oldcore-[6.4.1]] is inc ompatible with the core extension [org.xwiki.platform:xwiki-platform-legacy-oldcore-6.4.2]) 2015-03-05 08:05:49,031 [pool-2-thread-1] INFO o.x.s.s.i.EmbeddedSolrInstance - Starting embedded Solr server... 2015-03-05 08:05:49,040 [pool-2-thread-1] INFO o.x.s.s.i.EmbeddedSolrInstance - Using Solr home directory: [/var/cache/tomcat7/Catalina/loc alhost/Wiki/solr] 2015-03-05 08:05:53,881 [coreLoadExecutor-5-thread-1] WARN o.a.s.c.RequestHandlers - Multiple requestHandler registered to the same name: /update ignoring: org.apache.solr.handler.UpdateRequestHandler 2015-03-05 08:06:00,024 [pool-2-thread-1] INFO o.x.s.s.i.EmbeddedSolrInstance - Started embedded Solr server. Mar 05, 2015 8:06:02 AM org.apache.coyote.AbstractProtocol startphp5-pdo php5-pdo_mysql php5-memcache php5-curl php5-mbstring php-apc php-so ap php-imap memcached php-gd php-pear Kaj -- View this message in context: http://xwiki.475771.n2.nabble.com/Installed-version-6-4-1-is-not-valid-tp759... Sent from the XWiki- Users mailing list archive at Nabble.com.