this is probably just a band aid, but should at least

help figure out where my last crash came from by being
extra careful arround Add for scene object group.

OpenSim/Region/Environment/Scenes/SceneObjectGroup.cs

@@ -1635,9 +1635,15 @@ namespace OpenSim.Region.Environment.Scenes
         /// <param name="part"></param>
         public void AddPart(SceneObjectPart part)
         {
+            lock (m_parts) {
                 part.SetParent(this);
                 part.LinkNum = m_parts.Count;
+                try {
                     m_parts.Add(part.UUID, part);
+                } catch (Exception e) {
+                    m_log.Error("Failed to add scened object part", e);
+                }
+            }
         }
 
         /// <summary>