[xwiki-users] Impossible to create users and groups in a slave wiki of XEM 2.4

Hi, Just done a fresh install of XEM2.4 and I encounter the following problem. In the templatexe wiki, it's impossible to add a new group or a new user (the Add button do nothing). If I edit the objects of an existing group (XWikiAllGroup for example), a warning is displayed : "Some objects from this document contain deprecated properties which were deleted from their respective classes." In fact, I detected that the *XWikiGroups and XWikiUsers classes are not defined* (they do not exist) in this templatexe wiki. In the main wiki, all is ok (and the XWikiGroups and Users classes are well defined). Nothing in the xwiki.log. Do you have any idea to help me ? Best regards, Maxime Mathieu