DHCP Client Service causes slow uploads

Running windows xp pro on multiple workstations...when attempting to transfer data to our Windows 2003 SMB Premium server we are receiving extremely slow transfer rates (about 1-5% network utilization) while the Microsoft Explorer window is open. Transfer from workstation to workstation is fine and transfer from the server to the workstation is normal as well, only transfer to the server is causing a problem.

Stopped all, but the following services on the server: DHCP Client, Event log, plug and play, rpc, sb core service, scanmail monitor, security accounts manager, server, terminal services, win http web prox auto-disc, workstation.

The issue still persisted, so I tried the following on the workstations. Opened the explorer window and tried copying to the server, same issue...so I started disabling services. When I disabled the dhcp client service, my connection to the server was lost, so I restarted it and tried copying files again. The files copied at normal rates (around 50-60% network utilization). However, if i close the open explorer window and open a new one up to copy files, the issue reoccurs until i stop the dhcp client service and restart it again with the current window open.

I can also get appropriate transfer rates by starting the copy and then closing the explorer window. The rates will jump from 1% to around 50-60% after the explorer window is closed.

Any assistance with this matter would be appreciated.