persistent access rights issues

Dear all, I am still looking for a solution to this problem I have (see below). The trouble happens in what seems to be a basic use of the XWiki. Does not somebody else experienced the same problem? Any insights would be welcome...The wiki is still public at http://biodiversite.xwiki.com. I have found what seems to be another bug. When I login as guest, password guest, the xwiki front page, welcome me as Alexandre-Benjamin, somebody I do not know at all!! All ideas welcome, --------------- dear all, I am having trouble restricting the access of a document to my XWiki registered users only. If I apply the edit, view rights to XWiki.XWikiAllGroup at the last document published, I get the following error message when logout : Error number 4001 in 4: Error while parsing velocity page Main.WebHome Wrapped Exception: Invocation of method 'formatDate' in class com.xpn.xwiki.api.XWiki threw exception class java.lang.NullPointerException : null While when I do the same for an older document, this document is effectively hidden when I logout but the others appear in double! Any idea? Many thanks in advance, -- Arnaud Béchet Station biologique de la Tour du Valat Le Sambuc - 13 200 Arles - France Tel : +33 (0)4 90 97 29 73 Fax : +33 (0)4 90 97 20 19 www.tourduvalat.org