Performance Issue Between W2K3 Server & Windows Explorer

W2K3 Server OS (Domain Controller & SQL Server 2000)on
Dell Poweredge 2650
WinXP-Pro PC

Basic file copies from PC to server via Windows Explorer
are fast, however, if I simply access a server file via
Windows Explorer from my PC and then turn around and
perform another file copy from PC to server via Windows
Explorer, it is very, very slow. If I close Windows
Explorer and reopen it, everything is fast again, that is
until the next time I access a file residing on the server
through Windows Explorer.

Troubleshooting steps Performed:
-All updates applied to server and PC.
-I had mapped network drives via MMC scripting (*.bat);
however, when this problem surfaced I reconfigured PC to
static drive mappings, no change in problem.
-I stopped DHCP on server and configured PC for static IP.
-It is a local server not broadcasting externally,
therefore, DNS has no forward or reverse lookup zones,
fqdn example: w2k3.microsoftnetwork.local
-Disabled second GBIC NIC and currently running with a
single card as they were bridged and balanced.
-Replaced cable from server to switch.
-Replaced cable from PC to switch.


If anybody can provide any suggestions It would be greatly
appreciated as this problem described does not take place
on W2K server, only W2K3 server and it's driving me crazy!

TIA,
Bryan