java.util.ConcurrentModificationException
        at org.openide.util.WeakSet$WeakSetIterator.checkModcount(WeakSet.java:481)
        at org.openide.util.WeakSet$WeakSetIterator.hasNext(WeakSet.java:432)
        at org.netbeans.modules.project.ui.ProjectsRootNode.checkNoLazyNode(ProjectsRootNode.java:205)
        at org.netbeans.modules.project.ui.OpenProjectList$LoadOpenProjects.run(OpenProjectList.java:318)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:573)
        at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1005)