[xwiki-users] Lucene stopped (and does not restart) after upgrade from 3.2 to 3.4

Hello, I have an XWIKI running 3.2 on Tomcat6 PostgreSQL. I did export the WIKI (around 70 Mbytes) to a XAR before upgrading to 3.4. To upgrade to 3.4 import did delete the XWIKI database and created a new blank one. I installed XWIKI 3.4 with the default .xar then used the XWIKI large import utility (http://extensions.xwiki.org/xwiki/bin/view/Extension/Large+XAR+Import) to reload my spaces from the XAR archive. (since importing doesn't work even after updating the max upload size and the JVM options). I all worked fine but Lucene does not index, even when I start Lucene indexing manually from 'Administer wiki'. The search pages shows' Lucene is currently building its index, 618 documents in queue". But it never moves from there. Please let me know what's going on and how I could restart Lucene. Many thanks for your help, Regards, Christophe FRAULE