[ns] problems with ns2.28 and mobiwan

[tqytan]

 
 Hi, I successfully install ns2.28 and mobiwan. I executed simple-mipv6 and got 
the result, but when I rana TCL script like /ns-2.28/tcl/ex/simple.tcl, I got 
the following error as shown below: 
   
  can't read "EnableHierRt_": no such variable
      (Object set line 1)
      invoked from within
  "Simulator set EnableHierRt_"
      (procedure "_o10" line 10)
      (Node attach line 10)
      invoked from within
  "$node attach $agent"
      (procedure "_o3" line 2)
      (Simulator attach-agent line 2)
      invoked from within
  "$ns attach-agent $n0 $udp0"
      (file "simple.tcl" line 29)

It seems that this is a bug introduced by ns-228-mobiwan-102. How can I handle 
this problem? 

Thanks a lot!