Do you get any errors or indications that changes are required when issuing the following (non-destructive, informational) Terminal.app command?
sudo changeip -checkhostname
Is the domain a real and registered domain, or is it a ".local" domain?
Is the configured server at a static IP address? (Either a static address on a private LAN, or a public static address.)
Is there exactly one DNS server or one pool of DNS servers, and is that DNS server or pool local? (Are there any references to other non-local-LAN DNS servers?)
Logs? Assuming the server isn't all that busy when you test, launch Console.app, start your connection test with the Server Tools, and look at the aggregate log display for errors. (If it's busier box and can't be quiesced for testing, then yes, you can have to drill down into individual logs, or grep -R the /var/log directory for server or such...) But without knowing what (else) is wrong, it's difficult to predict.
Thanks for the suggestions Mr. Hoffman.
The changeip had no changes (it was matched)
The domain is local, but not .local (i know enough not to do that). So the domain is myschool.lan.
DNS is successfull both fwd and reverse, with and without the .lan
Configured Static. One DNS server inside lan, with forwards to our ISP dns. Lookups work fine. No other refs.
Other strangeness I have noticed since....
ARD / Screen sharing stops working after some time (1 hour or so).
I have disk checked, repaired permissions, and nothing out of the oordinary.
I read somewhere starting in Single user mode, just simply doing that, can fix some issues.... I'll try next.
Any other suggestions?