diff --git a/OpenSim/Region/Framework/Scenes/Scene.cs b/OpenSim/Region/Framework/Scenes/Scene.cs
index 6c34056605..42051d07e1 100644
--- a/OpenSim/Region/Framework/Scenes/Scene.cs
+++ b/OpenSim/Region/Framework/Scenes/Scene.cs
@@ -120,7 +120,7 @@ namespace OpenSim.Region.Framework.Scenes
         private readonly Timer m_restartTimer = new Timer(15000); // Wait before firing
         private int m_incrementsof15seconds;
         private volatile bool m_backingup;
-        private bool m_useAsyncWhenPossible = true;
+        private bool m_useAsyncWhenPossible;
 
         private Dictionary<UUID, ReturnInfo> m_returns = new Dictionary<UUID, ReturnInfo>();
         private Dictionary<UUID, SceneObjectGroup> m_groupsWithTargets = new Dictionary<UUID, SceneObjectGroup>();
@@ -480,7 +480,7 @@ namespace OpenSim.Region.Framework.Scenes
                 IConfig startupConfig = m_config.Configs["Startup"];
 
                 // Should we try to run loops synchronously or asynchronously?
-                m_useAsyncWhenPossible = startupConfig.GetBoolean("use_async_when_possible", true);
+                m_useAsyncWhenPossible = startupConfig.GetBoolean("use_async_when_possible", false);
 
                 //Animation states
                 m_useFlySlow = startupConfig.GetBoolean("enableflyslow", false);
@@ -4261,10 +4261,13 @@ namespace OpenSim.Region.Framework.Scenes
 
         public void ForEachClient(Action<IClientAPI> action, bool doAsynchronous)
         {
-            if (doAsynchronous)
-                m_clientManager.ForEach(action);
-            else
-                m_clientManager.ForEachSync(action);
+            // FIXME: Asynchronous iteration is disabled until we have a threading model that
+            // can support calling this function from an async packet handler without
+            // potentially deadlocking
+            //if (doAsynchronous)
+            //    m_clientManager.ForEach(action);
+            //else
+            //    m_clientManager.ForEachSync(action);
         }
 
         public bool TryGetClient(UUID avatarID, out IClientAPI client)
diff --git a/bin/OpenSim.ini.example b/bin/OpenSim.ini.example
index 2adc87f440..4f1799e94c 100644
--- a/bin/OpenSim.ini.example
+++ b/bin/OpenSim.ini.example
@@ -49,7 +49,7 @@
     ; in parallel. Running in parallel should increase performance
     ; on a multi-core system, but will make debugging more
     ; difficult if something deadlocks or times out
-    use_async_when_possible = true
+    use_async_when_possible = false
     
     ; Max threads to allocate on the FireAndForget thread pool
     ; when running with the SmartThreadPool option above