When opening the Services Directory application or connecting to a web service, the following error message is returned:
"Identity Error: Server could not authenticate the supplied identity".
This issue applies to ArcGIS Server for the Microsoft .NET Framework.
The case of the username entered when running the Web Applications Post Install or AddInstance utility did not match the case of the existing user account.
There is a known issue, where the Services Directory application and Web services are performing a case sensitive comparison of the username.