java.util.ConcurrentModificationException
   at java.util.Hashtable$Enumerator.next(Hashtable.java:1081)
   at org.openide.util.NbCollections.checkedMapByCopy(NbCollections.java:151)
   at org.netbeans.spi.project.support.ant.ProjectProperties.getStockPropertyPreprovider(ProjectProperties.java:426)
   at org.netbeans.spi.project.support.ant.AntProjectHelper.getStockPropertyPreprovider(AntProjectHelper.java:1202)
   at org.netbeans.modules.java.j2seproject.J2SEProject.createEvaluator(J2SEProject.java:268)
   at org.netbeans.modules.java.j2seproject.J2SEProject.<init>(J2SEProject.java:215)
   at sun.reflect.GeneratedConstructorAccessor32.newInstance(GeneratedConstructorAccessor32.java:0)
   at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
   at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
   at org.netbeans.modules.project.ant.AntBasedGenericType.createProject(AntBasedGenericType.java:129)
   at org.netbeans.modules.project.ant.AntBasedProjectFactorySingleton.loadProject(AntBasedProjectFactorySingleton.java:266)
   at org.netbeans.api.project.ProjectManager.createProject(ProjectManager.java:365)
   at org.netbeans.api.project.ProjectManager.access$300(ProjectManager.java:85)
   at org.netbeans.api.project.ProjectManager$2.run(ProjectManager.java:286)
   at org.netbeans.api.project.ProjectManager$2.run(ProjectManager.java:233)
   at org.openide.util.Mutex.readAccess(Mutex.java:330)
   at org.netbeans.api.project.ProjectManager.findProject(ProjectManager.java:233)
   at org.netbeans.modules.projectapi.SimpleFileOwnerQueryImplementation.getOwner(SimpleFileOwnerQueryImplementation.java:131)
   at org.netbeans.api.project.FileOwnerQuery.getOwner(FileOwnerQuery.java:104)
   at org.netbeans.modules.project.ui.ProjectsRootNode$BadgingNode.setGroups(ProjectsRootNode.java:652)
   at org.netbeans.modules.project.ui.ProjectsRootNode$BadgingNode.setProjectFiles(ProjectsRootNode.java:630)
   at org.netbeans.modules.project.ui.ProjectsRootNode$BadgingNode.setProjectFiles(ProjectsRootNode.java:543)
   at org.netbeans.modules.project.ui.ProjectsRootNode$BadgingNode$2.run(ProjectsRootNode.java:480)
Caused: org.openide.util.RequestProcessor$SlowItem: task failed due to: java.util.ConcurrentModificationException
   at org.openide.util.RequestProcessor$Task.schedule(RequestProcessor.java:1465)
   at org.netbeans.modules.project.ui.ProjectsRootNode$BadgingNode.setProjectFilesAsynch(ProjectsRootNode.java:476)
   at org.netbeans.modules.project.ui.ProjectsRootNode$BadgingNode.replaceProject(ProjectsRootNode.java:607)
   at org.netbeans.modules.project.ui.ProjectsRootNode$BadgingNode.access$000(ProjectsRootNode.java:448)
   at org.netbeans.modules.project.ui.ProjectsRootNode.checkNoLazyNode(ProjectsRootNode.java:218)
   at org.netbeans.modules.project.ui.ProjectsRootNode.checkNoLazyNode(ProjectsRootNode.java:211)
   at org.netbeans.modules.project.ui.OpenProjectList$LoadOpenProjects.run(OpenProjectList.java:309)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1424)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1973)