I got the same error #user.authentication.userRequired## by changing the configuration parameter to Off as below works!
; This check will invalidate a session if the user’s IP address changes.
; Enabling this option provides some amount of additional security, but may
; cause problems for users behind a proxy farm (e.g., AOL).
session_check_ip = Off
Further great explanation go here What is "session_check_ip"?
Dung.