event id 1054 - Windows cannot obtain the domain controller name for your computer network

I have got 4 clients in a different building connected by fiber optic to ethernet adapter, linksys switch in both ends. Every morning they are down, I am finding the event id 1054 - Userenv - Windows cannot obtain the domain controller name for your computer network. (A socket operation was attempted to an unreachable host. ). Group Policy processing aborted. I have to reset linksys switch and fiber optic adapter to get the connection back. I have also tried replacing the linksys switch and it works until next morning. I have also upgraded to Service Pack 2 recently and I have already uninstalled and reinstalled them but still that didnt work for me. Also, I have removed the clients from the domain and added them from the Server Management but every morning I have to hard reset the switch and fiber optic converter. Any ideas?

As per my view, the problem that you are facing can occur if the DNS server isnt valid or reachable. Did you try to correct DNS settings on your server versus clients? Did the clients and the SBS as their DNS server? Does your DNS server has it self as its DNS server?

The problem occurs because link status fluctuates as the network adapter (also known as the network interface card, or NIC) driver initializes and as the network adapter hardware negotiates a link with the network infrastructure. The Group Policy application stack executes before the negotiation process is completed and can fail because of the absence of a valid link. For more information, go to this website - http://support.microsoft.com/kb/326152