Access denied error on server when Security mode="message"

Question

My WCF has 3 endpoints

1. webHttpBinding - for RESTFull pattern
2. wsHttpBinding - consumed by a VSTO plugin app. using service reference
3. mexHttpBinding.

In the bindings section of my app.config (server).

To configure security for RESTFull Service , this is how I configure

This works good and I have impersonation on , so I am able to get the requesting client's user name, which I pass on to my custom roles validator class.

Now , what I am trying to do is configure something similar for the wsHttpBinding.

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The server starts good.

From the client I try to access a folder on the server - something like Directory.Exists(path). Now this gives me "Access Denied".

Mind you my server and client are on the same machine , and the user is admin user.

Any hints or pointers to why this happens would be highly appreciated.

This is how my client applications binding looks like -

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