New install, XWikiPreferences doesn't work

Hi all, I've followed the install procedure for XWiki 1.1 milestone 3 - using HSQL and OC4J. It works in that I can go to /xwiki and I get a page 'XWiki Installation' with links to Installation Instructions and the XWiki Home Page. The next step according to the documentation is to import the default wiki XAR file. But when I go to: xwiki/bin/admin/XWiki/XWikiPreferences I get a '500 Internal Server Error' along with: 'Servlet error: An exception occurred. The current application deployment descriptors do not allow for including it in this response. Please consult the application log for details.' The xwiki.log file shows the following message: 11:24:11,716 [AJPRequestHandler-RMICallHandler-6] WARN action.RequestProcessor - Unhandled Exception thrown: class com.xpn.xwiki.XWikiException Any suggestions please? Thanks Neil