java.awt.dnd.InvalidDnDOperationException: Drag and drop in progress
   at sun.awt.dnd.SunDragSourceContextPeer.setDragDropInProgress(SunDragSourceContextPeer.java:358)
   at java.awt.dnd.DragSource.startDrag(DragSource.java:301)
   at java.awt.dnd.DragSource.startDrag(DragSource.java:396)
   at java.awt.dnd.DragGestureEvent.startDrag(DragGestureEvent.java:291)
   at org.netbeans.core.windows.view.dnd.TopComponentDragSupport.doStartDrag(TopComponentDragSupport.java:417)
   at org.netbeans.core.windows.view.dnd.TopComponentDragSupport.eventDispatched(TopComponentDragSupport.java:352)
   at java.awt.Toolkit$SelectiveAWTEventListener.eventDispatched(Toolkit.java:2440)
   at java.awt.Toolkit$ToolkitEventMulticaster.eventDispatched(Toolkit.java:2331)
   at java.awt.Toolkit$ToolkitEventMulticaster.eventDispatched(Toolkit.java:2331)
   at java.awt.Toolkit$ToolkitEventMulticaster.eventDispatched(Toolkit.java:2331)
   at java.awt.Toolkit$ToolkitEventMulticaster.eventDispatched(Toolkit.java:2331)
   at java.awt.Toolkit$ToolkitEventMulticaster.eventDispatched(Toolkit.java:2331)
   at java.awt.Toolkit$ToolkitEventMulticaster.eventDispatched(Toolkit.java:2331)
   at java.awt.Toolkit$ToolkitEventMulticaster.eventDispatched(Toolkit.java:2331)
   at java.awt.Toolkit$ToolkitEventMulticaster.eventDispatched(Toolkit.java:2331)
   at java.awt.Toolkit$ToolkitEventMulticaster.eventDispatched(Toolkit.java:2331)
   at java.awt.Toolkit$ToolkitEventMulticaster.eventDispatched(Toolkit.java:2331)
   at java.awt.Toolkit$ToolkitEventMulticaster.eventDispatched(Toolkit.java:2331)
   at java.awt.Toolkit$ToolkitEventMulticaster.eventDispatched(Toolkit.java:2331)
   at java.awt.Toolkit$ToolkitEventMulticaster.eventDispatched(Toolkit.java:2331)
   at java.awt.Toolkit.notifyAWTEventListeners(Toolkit.java:2290)
   at java.awt.Component.dispatchEventImpl(Component.java:4779)
   at java.awt.Container.dispatchEventImpl(Container.java:2292)
   at java.awt.Component.dispatchEvent(Component.java:4705)
   at java.awt.LightweightDispatcher.retargetMouseEvent(LightweightDispatcher.java:4898)
   at java.awt.LightweightDispatcher.processMouseEvent(LightweightDispatcher.java:4550)
   at java.awt.LightweightDispatcher.dispatchEvent(LightweightDispatcher.java:4462)
   at java.awt.Container.dispatchEventImpl(Container.java:2278)
   at java.awt.Window.dispatchEventImpl(Window.java:2739)
   at java.awt.Component.dispatchEvent(Component.java:4705)
   at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:746)
   at java.awt.EventQueue.access$400(EventQueue.java:97)
   at java.awt.EventQueue$3.run(EventQueue.java:697)
   at java.awt.EventQueue$3.run(EventQueue.java:691)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
   at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86)
   at java.awt.EventQueue$4.run(EventQueue.java:719)
   at java.awt.EventQueue$4.run(EventQueue.java:717)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:716)
   at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:159)
   at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
   at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
   at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
   at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)