Not a very clear error message. To get a clear message you can add the following to the web.config in the <serviceBehaviors> section for each <behavior>:
<serviceSecurityAudit auditLogLocation="Application" serviceAuthorizationAuditLevel="Failure" messageAuthenticationAuditLevel="Failure" suppressAuditFailure="true" />
Now I get a clear message in the Application EventLog:
Message authentication failed. Service: https://xxxxxxxxxxxxxxx.svc Action: http://schemas.xmlsoap.org/ws/2005/02/trust/RST/SCT ClientIdentity: ActivityId: FileNotFoundException: Could not load file or assembly 'Oracle.DataAccess, Version=4.112.2.0, Culture=neutral, PublicKeyToken=89b483f429c47342' or one of its dependencies. The system cannot find the file specified.
Always the Oracle DLL's... My next blog post will show the solution to this problem.
Remember to remove this line from the web.config on production systems, because it implies a performance impact.