java.lang.IllegalStateException: Problem in some module which uses Window System: Window System API is required to be called from AWT thread only, see http://core.netbeans.org/proposals/threading/
   at org.netbeans.core.windows.WindowManagerImpl.warnIfNotInEDT(WindowManagerImpl.java:1520)
   at org.netbeans.core.windows.WindowManagerImpl.topComponentID(WindowManagerImpl.java:1215)
   at org.openide.windows.WindowManager.findTopComponentID(WindowManager.java:529)
   at org.netbeans.core.windows.model.TopComponentSubModel.getID(TopComponentSubModel.java:367)
   at org.netbeans.core.windows.model.TopComponentSubModel.setSelectedTopComponent(TopComponentSubModel.java:309)
   at org.netbeans.core.windows.model.DefaultModeModel.setSelectedTopComponent(DefaultModeModel.java:174)
   at org.netbeans.core.windows.model.DefaultModel.setModeSelectedTopComponent(DefaultModel.java:623)
   at org.netbeans.core.windows.Central.activateModeTopComponent(Central.java:1761)
   at org.netbeans.core.windows.WindowManagerImpl.topComponentRequestActive(WindowManagerImpl.java:1148)
   at org.openide.windows.TopComponent.requestActive(TopComponent.java:871)
   at org.netbeans.modules.visualgc.actions.ShowVisualGCAction.actionPerformed(ShowVisualGCAction.java:55)
   at org.netbeans.modules.visualgc.actions.ShowVisualGCAction.<init>(ShowVisualGCAction.java:44)
   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.openide.loaders.InstanceSupport.instanceCreate(InstanceSupport.java:222)
   at org.openide.loaders.InstanceDataObject$Ser.instanceCreate(InstanceDataObject.java:1383)
   at org.openide.loaders.InstanceDataObject.instanceCreate(InstanceDataObject.java:821)
   at org.openide.loaders.FolderInstance.instanceForCookie(FolderInstance.java:588)
   at org.openide.awt.MenuBar$LazyMenu$MenuFolder.instanceForCookie(MenuBar.java:697)
   at org.openide.loaders.FolderInstance$HoldInstance.instanceCreate(FolderInstance.java:1138)
   at org.openide.loaders.FolderInstance$1R.instances(FolderInstance.java:708)
   at org.openide.loaders.FolderInstance$1R.run(FolderInstance.java:729)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1424)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1968)