VirtualBox Failed to negotiate protocol, retrying with plain RDP.

Hello,

I use
  "Version 1.8.1. Copyright (C) 1999-2011 Matthew Chapman et al."

and
  Oracle VM VirtualBox Manager 4.3.8

After enabling "remote display" in a virtual machine, when I try to 
connect to it I get the message :
  "Failed to negotiate protocol, retrying with plain RDP."

Are you aware of this bug ?

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