Question : No Logon Servers Available to service the request

Hello,
We have been having difficulty in our network in which i work part time on.
We have a Windows 2003  Server and one W2K server with mostly W2K Clients (around 20) and some Xp Pro clients (around 5)
W2K server only authenticates clients in the domain (PDC) for the domain we have the clients connected to. We also have installed Norton Antivirus Corporate in the W2K server and nothing else.
The Windows 2003 server holds most of the applications eg: rightfax, postcast Server, etc and we have a lot of shared files in the Windows 2003 server that are needed to be accesed from network neighborhood. However when I try to log in from an XP or W2K client to that specific Windows 2003 server OR any other client in the network logged in as an administrator i get the message:
\\server is not available. You might not have permission to access this network resource. Contact the administrator of this server to find out if you have access permissions. THERE ARE CURRENTLY NO LOGON SERVERS AVAILABLE TO SERVICE THE LOGON REQUEST.
This happens for a while and after a certain period of time (hour or 2 or so) If I try to access the server from the same XP pro client again after that period of time it then prompts me for the username and password of the windows 2003 server that I am trying to access and it finally lets me in. However if I immediately log off and log back in using the same account (adminstrator) it starts to prompt me for the same error message.
Most of the clients are using Dynamic IP configuration and some are using static ip's.
Most of the most obvious troubleshooting has been done but it doesn't seem to help.

Any ideas would be greatly appreciated.
Thanks

Answer : No Logon Servers Available to service the request

Hello

So when you log on to the domain you cannot access the server and it asks for authentication, but if you log on to a machine locally and supply a password it works ok ? Bit of a strange issue. I would check the server event logs for any information relating to this problem as well as on the workstation, possibly try disjoining and rejoining the domain. Im assuming that clients that are obtaining dhcp addresses are pointing to a valid dns server for your domain.

Hope this helps