java.awt.dnd.InvalidDnDOperationException: Drag and drop in progress
        at sun.awt.dnd.SunDragSourceContextPeer.setDragDropInProgress(SunDragSourceContextPeer.java:313)
        at java.awt.dnd.DragSource.startDrag(DragSource.java:285)
        at java.awt.dnd.DragSource.startDrag(DragSource.java:402)
        at java.awt.dnd.DragGestureEvent.startDrag(DragGestureEvent.java:221)
        at org.openide.explorer.view.ExplorerDragSupport.dragGestureRecognized(ExplorerDragSupport.java:109)
        at org.openide.explorer.view.TreeViewDragSupport.dragGestureRecognized(TreeViewDragSupport.java:74)
        at java.awt.dnd.DragGestureRecognizer.fireDragGestureRecognized(DragGestureRecognizer.java:339)
        at sun.awt.windows.WMouseDragGestureRecognizer.mouseDragged(WMouseDragGestureRecognizer.java:205)
        at java.awt.AWTEventMulticaster.mouseDragged(AWTEventMulticaster.java:258)
        at java.awt.AWTEventMulticaster.mouseDragged(AWTEventMulticaster.java:257)
        at java.awt.AWTEventMulticaster.mouseDragged(AWTEventMulticaster.java:257)
        at java.awt.AWTEventMulticaster.mouseDragged(AWTEventMulticaster.java:257)
        at java.awt.AWTEventMulticaster.mouseDragged(AWTEventMulticaster.java:257)
        at java.awt.AWTEventMulticaster.mouseDragged(AWTEventMulticaster.java:257)
        at java.awt.AWTEventMulticaster.mouseDragged(AWTEventMulticaster.java:257)
        at java.awt.AWTEventMulticaster.mouseDragged(AWTEventMulticaster.java:257)
        at java.awt.Component.processMouseMotionEvent(Component.java:5069)
        at javax.swing.JComponent.processMouseMotionEvent(JComponent.java:2763)
        at java.awt.Component.processEvent(Component.java:4822)
        at java.awt.Container.processEvent(Container.java:1380)
        at java.awt.Component.dispatchEventImpl(Component.java:3526)
        at java.awt.Container.dispatchEventImpl(Container.java:1437)
        at java.awt.Component.dispatchEvent(Component.java:3367)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3214)
[catch] at java.awt.LightweightDispatcher.processMouseEvent(Container.java:2946)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:2859)
        at java.awt.Container.dispatchEventImpl(Container.java:1423)
        at java.awt.Window.dispatchEventImpl(Window.java:1566)
        at java.awt.Component.dispatchEvent(Component.java:3367)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:445)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:190)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:144)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:130)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:98)