I've created some groups as admin, everything was ok. After a couple of days I figured out that I need to move the groups I've created under a more general group as subgroups. I didn't found such functionality, so I've started deleting the groups in order to create new sub-groups..
But, when only one group remained, Alfresco didn't want to work anymore (even clicking on the logout button) for the current session, displaying the following error on every page. (I've reopened the browser and was able to login as admin and delete the last group that remained. So, Alfresco is working now, I just wanted to let you know about the error).
javax.faces.el.PropertyNotFoundException: Bean: org.alfresco.web.bean.groups.CreateGroupDialog, property: groupsRichList
javax.faces.el.PropertyNotFoundException: Bean: org.alfresco.web.bean.groups.CreateGroupDialog, property: groupsRichList
at org.apache.myfaces.el.PropertyResolverImpl.getPropertyDescriptor(PropertyResolverImpl.java:500)
at org.apache.myfaces.el.PropertyResolverImpl.getPropertyDescriptor(PropertyResolverImpl.java:472)
at org.apache.myfaces.el.PropertyResolverImpl.setProperty(PropertyResolverImpl.java:388)
at org.apache.myfaces.el.PropertyResolverImpl.setValue(PropertyResolverImpl.java:176)
at org.apache.myfaces.el.ValueBindingImpl.setValue(ValueBindingImpl.java:278)
at org.apache.myfaces.shared_impl.util.RestoreStateUtils.recursivelyHandleComponentReferencesAndSetValid(RestoreStateUtils.java:86)
at org.apache.myfaces.shared_impl.util.RestoreStateUtils.recursivelyHandleComponentReferencesAndSetValid(RestoreStateUtils.java:57)
at org.apache.myfaces.shared_impl.util.RestoreStateUtils.recursivelyHandleComponentReferencesAndSetValid(RestoreStateUtils.java:94)
at org.apache.myfaces.shared_impl.util.RestoreStateUtils.recursivelyHandleComponentReferencesAndSetValid(RestoreStateUtils.java:57)
at org.apache.myfaces.shared_impl.util.RestoreStateUtils.recursivelyHandleComponentReferencesAndSetValid(RestoreStateUtils.java:94)
at org.apache.myfaces.shared_impl.util.RestoreStateUtils.recursivelyHandleComponentReferencesAndSetValid(RestoreStateUtils.java:57)
at org.apache.myfaces.shared_impl.util.RestoreStateUtils.recursivelyHandleComponentReferencesAndSetValid(RestoreStateUtils.java:94)
at org.apache.myfaces.shared_impl.util.RestoreStateUtils.recursivelyHandleComponentReferencesAndSetValid(RestoreStateUtils.java:57)
at org.apache.myfaces.lifecycle.RestoreViewExecutor.execute(RestoreViewExecutor.java:96)
at org.apache.myfaces.lifecycle.LifecycleImpl.executePhase(LifecycleImpl.java:95)
at org.apache.myfaces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:70)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:139)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at org.alfresco.web.app.servlet.AuthenticationFilter.doFilter(AuthenticationFilter.java:81)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:870)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685)
at java.lang.Thread.run(Thread.java:619)