diff -r 791a1b447304 src/core/test/threaded-test-suite.cc
--- a/src/core/test/threaded-test-suite.cc	Sat Mar 31 10:02:25 2012 +0200
+++ b/src/core/test/threaded-test-suite.cc	Tue Apr 24 16:03:22 2012 +0200
@@ -196,7 +196,7 @@
       m_threadlist.push_back(
         Create<SystemThread> (MakeBoundCallback (
             &ThreadedSimulatorEventsTestCase::SchedulingThread, 
-                std::pair<ThreadedSimulatorEventsTestCase *, unsigned int>(this,1) )) );
+                std::pair<ThreadedSimulatorEventsTestCase *, unsigned int>(this,i) )) );
     }
 }
 void 
@@ -209,6 +209,7 @@
 void 
 ThreadedSimulatorEventsTestCase::DoRun (void)
 {
+  m_stop = false;
   Simulator::SetScheduler (m_schedulerFactory);
 
   Simulator::Schedule (MicroSeconds (10), &ThreadedSimulatorEventsTestCase::A, this, 1);
@@ -219,12 +220,9 @@
     {
       (*it)->Start();
     }
-  
   Simulator::Run ();
   Simulator::Destroy ();
 
-  m_stop = true;
-
   NS_TEST_EXPECT_MSG_EQ (m_error.empty(), true, m_error.c_str());
   NS_TEST_EXPECT_MSG_EQ (m_a, m_b, "Bad scheduling");
   NS_TEST_EXPECT_MSG_EQ (m_a, m_c, "Bad scheduling");
diff -r 791a1b447304 src/visualizer/model/pyviz.cc
--- a/src/visualizer/model/pyviz.cc	Sat Mar 31 10:02:25 2012 +0200
+++ b/src/visualizer/model/pyviz.cc	Tue Apr 24 16:03:22 2012 +0200
@@ -265,8 +265,11 @@
 PyViz::CallbackStopSimulation ()
 {
   NS_LOG_FUNCTION_NOARGS ();
-  Simulator::Stop (Seconds (0)); // Stop right now
-  m_stop = true;
+  if (m_runUntil <= Simulator::Now ())
+    {
+      Simulator::Stop (Seconds (0)); // Stop right now
+      m_stop = true;
+    }
 }
 
 void
@@ -316,20 +319,11 @@
   // sure we stop at the right time.  Otherwise, simulations with few
   // events just appear to "jump" big chunks of time.
   NS_LOG_LOGIC ("Schedule dummy callback to be called in " << (time - Simulator::Now ()));
+  m_runUntil = time;
   m_stop = false;
-  Simulator::Cancel (m_stopCallbackEvent);
-  m_stopCallbackEvent = Simulator::Schedule (time - Simulator::Now (), &PyViz::CallbackStopSimulation, this);
+  Simulator::ScheduleWithContext (0xffffffff, time - Simulator::Now (), &PyViz::CallbackStopSimulation, this);
 
-  Ptr<SimulatorImpl> impl = Simulator::GetImplementation ();
-  Ptr<VisualSimulatorImpl> visualImpl = DynamicCast<VisualSimulatorImpl> (impl);
-  if (visualImpl)
-    {
-      visualImpl->RunRealSimulator ();
-    }
-  else
-    {
-      impl->Run ();
-    }
+  Simulator::Run()
 }
 
 bool PyViz::TransmissionSampleKey::operator < (PyViz::TransmissionSampleKey const &other) const
diff -r 791a1b447304 src/visualizer/model/pyviz.h
--- a/src/visualizer/model/pyviz.h	Sat Mar 31 10:02:25 2012 +0200
+++ b/src/visualizer/model/pyviz.h	Tue Apr 24 16:03:22 2012 +0200
@@ -220,7 +220,7 @@
   void DoPause (std::string const &message);
 
   bool m_stop;
-  EventId m_stopCallbackEvent;
+  Time m_runUntil;
   void CallbackStopSimulation ();
 };