I have Windows/External Authentication working on filemaker server 9 with 8.5 clients, but every once and a while, about every other week, the external authentication will stop working and the filemaker server service will lock up not allowing any databases to be served. If I start the service from the Admin Console, it goes green from red, but authentication still doesn't work and users are promped for a password. The only solution is to reboot the entire server and it starts working again.
Also, before rebooting and after restarting the server service, I receive multiple EVENT ID 672 on my Event Viewer. It is titled.