I didn’t see this sooner, you probably reformatted the server by now or something but this might benefit someone else…
I have had this problem crop up on a couple of servers I’ve set up. It turned out that the NetInfo database was corrupted. There is a tech article on Apple’s support site that details how to restore from a backup. If you don’t manually backup your NetInfo databases they’re probably screwed anyway since the automatic backup writes over the last at 3:15AM…even if the database is damaged.
HTH