WCF Client Inner Exception: "The Security Support Provider Interface (SSPI) negotiation failed."

Creating a WCF Client in Visual Studio 2010, I struggled with this error.  I was running as the currently logged on user and the service was as well so this made no sense to me.  I found that this entry in the client app.config was the culprit: <identity><userPrincipalName value=”MYDOMAIN\MyUsername” /></identity> Simply deleting these 3 lines…

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