I get this error when I register my quickfields agent in webadmin.
This line from the event viewer on the webadmin server looks important to me. The full error is attached.
System.ServiceModel.Security.SecurityNegotiationException: A call to SSPI failed, see inner exception. ---> System.Security.Authentication.AuthenticationException: A call to SSPI failed, see inner exception. ---> System.ComponentModel.Win32Exception: The target principal name is incorrect