Remoting Impersonation/Delegation problem

Hi,
    I am working on a n-tier app using remoting. I am using the VS 2005 beta
2. My server needs to access a remote resources on behalf on the connected
user.

    I have configured my server like :
        <channel ref="tcp" secure="true" port="8081" impersonate="true">

    and my client:
        <channel ref="tcp" port="0" secure="true"
tokenImpersonationLevel="Delegation">

    I start my server in the context of UserA on one machine and the client
app on another using UserB. When I trace I can see that the context is
properly passed to the server application:
    WindowsIdentity currentUser = WindowsIdentity.GetCurrent();
  this return a WindowsIdentity for UserB, but the
currentUser.ImpersonationLevel is always 'Impersonation' I cannot get a
delegation token!!!!

    I have made sure that UserB is configured in AD to handle Delegation. I
must be missing something!!!!!

    Is there some privileges that I need to activate on my server

    Any ideas would be welcome!

Best regards