XP and Windows 200 Server

Has anyone came across this issue? I have an XP machine that logs in to a Windows 2000 Server with Active Directory. When I try to copy large files from my XP machine to the network drive, halfway through the copying it will error out. A dialog box pops up and it states “error copying file, specified network resource is no longer available” WIN 2000 server has SP3 and XP has SP1