* Re-applied r7223

OpenSim/Region/Environment/Scenes/Scene.cs

@@ -163,6 +163,8 @@ namespace OpenSim.Region.Environment.Scenes
         private Thread HeartbeatThread;
         private volatile bool shuttingdown = false;
 
+	private object m_deleting_scene_object = new object();
+
         #endregion
 
         #region Properties
@@ -1823,7 +1825,11 @@ namespace OpenSim.Region.Environment.Scenes
         {
             //SceneObjectPart rootPart = group.GetChildPart(group.UUID);
 
-            group.RemoveScriptInstances();
+	    // Serialise calls to RemoveScriptInstances to avoid
+	    // deadlocking on m_parts inside SceneObjectGroup
+	    lock (m_deleting_scene_object) {
+		group.RemoveScriptInstances();
+	    }
 
             foreach (SceneObjectPart part in group.Children.Values)
             {