java.util.ConcurrentModificationException
        at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372)
        at java.util.AbstractList$Itr.next(AbstractList.java:343)
        at org.netbeans.modules.debugger.jpda.models.ThreadsCache.setVirtualMachine(ThreadsCache.java:133)
        at org.netbeans.modules.debugger.jpda.JPDADebuggerImpl.setRunning(JPDADebuggerImpl.java:1316)
        at org.netbeans.modules.debugger.jpda.actions.StartActionProvider.doStartDebugger(StartActionProvider.java:203)
        at org.netbeans.modules.debugger.jpda.actions.StartActionProvider.access$100(StartActionProvider.java:73)
        at org.netbeans.modules.debugger.jpda.actions.StartActionProvider$1.run(StartActionProvider.java:163)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:577)
        at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1030)