event id 1054 - 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 4 clients in a different building connected by fiber optic to
ethernet adapter, linksys switch in both ends. Every morning they are
down, I find 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've tried replacing the linksys switch and works
until next morning.
Recently, I update to SP2. I have uninstalled SP2 and SP1 and
reinstalled them and make no difference. Also, have the clients remove
from the domain and add them from the Server Management but every
morning I have to hard reset the switch and fiber optic converter. Is
this sound familiar to anyone?
.