I have a network that has a Windows Server 2003 (Enterpise edition) working as a file server and it's also the AD domain controller. I have clients that include domain-member XP PCs and Macs and non-domain member PCs using the Guest account on the server. The network is running with a separate DHCP server (LinkSys) and Gigabit LAN cards on all PCs and MACs. All the functions appear to work normally....
I have a 5Gig file that I saved to the server from an XP PC and I can't read it back from the server to the PCs without the following error "Cannot Copy <filename>:The specified network name is no longer available" appearing after maybe 30 seconds. I proved that this also happens if copying folders that contain large amounts of data so it's not that specific file and it doesn't matter if it's a domain member PC or not.
I'm using windows explorer and mapping a network drive to the server. When starting the transfer, the server network card is maxing out on transfer rates but apears to stop and then, maybe 20 seconds later, the client PC pops up the "Cannot Copy <filename>:The specified network name is no longer available" error message - annoyingly, file explorer never seems to lose its connection to the server and I can still explore the remote file share immediately after the message - i.e. the connection is still there. There appear to be no significant errors in any of the server or client access logs. A MAC (OS X) can copy the file to it's hard drive without errors but watching the network card activity on the server shows that there are gaps where the data transfer rate drops to almost zero and then picks up again - the file copies without error though.