The AuthentiX message is a general message that is created when the system is restarted.
Itcould be because the IIS6 default pool restarts itself once a day.
If the restart is happening randomly, but frequently, most likely there is an asp or .NET application that is choking or crashing IIS or one of its application pools. Then the automatic recovery system will restart IIS or the pool, and you will see the AuthentiX startup messages.
It doesn't indicate a problem with AuthentiX though.
If this happens very frequently, then the cause of the problem could be related to the Red Worm Patch:
"Speaking of patches, I've read several recent posts on the Bugtraq mailing list that indicate a problem might exist with the Microsoft patch listed in Microsoft Bulletin MS01-033. A few people have reported that after they installed the patch, their systems remain immune to Code Red infection. However, when an infected system attempts to connect to their system to infect it, several IIS services (e.g., FTP, the default Web site, the administrative Web site, and the proxy service) stop processing." - Windows Security Update