Getting Error when clicking on Users/Groups Tab

HTTP ERROR 500

Problem accessing /user-summary.jsp. Reason:

org.jivesoftware.util.cache.DefaultCache cannot be cast to com.jivesoftware.util.cache.ClusteredCache

Caused by:

java.lang.ClassCastException: org.jivesoftware.util.cache.DefaultCache cannot be cast to com.jivesoftware.util.cache.ClusteredCache     at com.jivesoftware.util.cache.CoherenceClusteredCacheFactory.getLock(CoherenceClusteredCacheFactory.java:351)     at org.jivesoftware.util.cache.CacheFactory.getLock(CacheFactory.java:378)     at org.jivesoftware.openfire.spi.PresenceManagerImpl.loadOfflinePresence(PresenceManagerImpl.java:551)     at org.jivesoftware.openfire.spi.PresenceManagerImpl.getLastActivity(PresenceManagerImpl.java:177)     at org.jivesoftware.openfire.admin.user_002dsummary_jsp._jspService(user_002dsummary_jsp.java:369)     at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)     at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)     at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:530)     at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1216)     at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:118)     at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:52)     at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1187)     at org.jivesoftware.util.LocaleFilter.doFilter(LocaleFilter.java:74)     at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1187)     at org.jivesoftware.util.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:50)     at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1187)     at org.jivesoftware.admin.PluginFilter.doFilter(PluginFilter.java:78)     at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1187)     at org.jivesoftware.admin.AuthCheckFilter.doFilter(AuthCheckFilter.java:164)     at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1187)     at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:425)     at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:119)     at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:494)     at org.eclipse.jetty.server.session.SessionHandler.handle(SessionHandler.java:182)     at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:933)     at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:362)     at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:867)     at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:117)     at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:245)     at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:126)     at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:113)     at org.eclipse.jetty.server.Server.handle(Server.java:334)     at org.eclipse.jetty.server.HttpConnection.handleRequest(HttpConnection.java:559)     at org.eclipse.jetty.server.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:992)     at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:541)     at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:203)     at org.eclipse.jetty.server.HttpConnection.handle(HttpConnection.java:406)     at org.eclipse.jetty.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:462)     at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:436)     at java.lang.Thread.run(Thread.java:636)

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when i uninstall the clustering plugins , then everything work fine.