java.util.ConcurrentModificationException
   at java.util.Hashtable$Enumerator.next(Hashtable.java:1031)
   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:255)
   at org.netbeans.modules.java.j2seproject.J2SEProject.<init>(J2SEProject.java:200)
   at sun.reflect.NativeConstructorAccessorImpl.newInstance0(NativeConstructorAccessorImpl.java:0)
   at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
   at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
   at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
   at org.netbeans.modules.project.ant.AntBasedGenericType.createProject(AntBasedGenericType.java:129)
   at org.netbeans.modules.project.ant.AntBasedProjectFactorySingleton.loadProject(AntBasedProjectFactorySingleton.java:267)
   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.csl.core.ProjectClassPathProvider.findClassPath(ProjectClassPathProvider.java:66)
   at org.netbeans.api.java.classpath.ClassPath.getClassPath(ClassPath.java:632)
   at org.netbeans.modules.parsing.impl.indexing.errors.ErrorAnnotator$1.run(ErrorAnnotator.java:309)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1424)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1968)