HG IM in grid mode working fairly well. Unknown target user references looked back in source user's User Agent service.

OpenSim/Server/Base/ServerUtils.cs

@@ -65,6 +65,10 @@ namespace OpenSim.Server.Base
         /// <returns></returns>
         public static T LoadPlugin<T>(string dllName, Object[] args) where T:class
         {
+            // This is good to debug configuration problems
+            //if (dllName == string.Empty)
+            //    Util.PrintCallStack();
+
             string[] parts = dllName.Split(new char[] {':'});
 
             dllName = parts[0];