Clustering plugin error after install it

hello,

when I click on clustering link in admin gui,

it shows

java.lang.NoClassDefFoundError: com/tangosol/net/Invocable
     at java.lang.Class.forName0(Native Method)
     at java.lang.Class.forName(Unknown Source)
     at org.jivesoftware.util.cache.CacheFactory.getMaxClusterNodes(CacheFactory.java:465)
     at org.jivesoftware.openfire.cluster.ClusterManager.getMaxClusterNodes(ClusterManager.java:384)
     at org.jivesoftware.openfire.admin.system_002dclustering_jsp._jspService(system_002dclustering_jsp.java:117)
     at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
     at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487)
     at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1093)
     at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:118)
     at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:52)
     at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084)
     at org.jivesoftware.util.LocaleFilter.doFilter(LocaleFilter.java:66)
     at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084)
     at org.jivesoftware.util.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:42)
     at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084)
     at org.jivesoftware.admin.PluginFilter.doFilter(PluginFilter.java:70)
     at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084)
     at org.jivesoftware.admin.AuthCheckFilter.doFilter(AuthCheckFilter.java:146)
     at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084)
     at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:360)
     at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
     at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181)
     at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:726)
     at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405)
     at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:206)
     at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114)
     at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
     at org.mortbay.jetty.Server.handle(Server.java:324)
     at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:505)
     at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:829)
     at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:514)
     at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:211)
     at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:380)
     at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:395)
     at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:488)

Linux Intel Fedora 10 64bits

maybe it’s a duplicate thread , sorry if it is

Thanks for your help