Here's the story:

public Action updateHit (Task task, long address)
    {
      if (address != this.address)
        {
          System.out.println("Hit wrong address!");
          return Action.CONTINUE;
        }
      else
        {
          cleanUpBreakPoint(task);
          task.requestDeleteCodeObserver(this, address);
        }

      triggered++;
      return Action.CONTINUE;
    }


If "task.requestDeleteCodeObserver(this, address);" is removed, then the 
following core state error does not occur.


{frysk.proc.LinuxPtraceTask@394a229d,pid=17918,tid=17918,state=detaching} in 
state "detaching" did not handle handleTrappedEvent

frysk.proc.State.unhandled(FryskGui)
frysk.proc.TaskState.handleTrappedEvent(FryskGui)
frysk.proc.Task.processTrappedEvent(FryskGui)
frysk.proc.LinuxPtraceHost$PollWaitOnSigChld$5.stopped(FryskGui)
frysk.sys.Wait.waitAllNoHang(FryskGui)
frysk.proc.LinuxPtraceHost$PollWaitOnSigChld.execute(FryskGui)
frysk.event.EventLoop.runEventLoop(FryskGui)
frysk.event.EventLoop.run(FryskGui)
frysk.gui.Gui$3.run(FryskGui)
java.lang.Thread.run(libgcj.so.7rh)