Offline Folders slow using NT Server

We are running Windows 2000 Prof workstation that connect to a Windows NT4.0 Server domain. Remote users (using broadband) try to open a file from the offline folder notice delays of a minute or more to open the file. Microsoft claims the file will be opened from the local cached copy first then the network (I suspect this is the case when connecting to a Windows 2000 Server). They need to physically unplug the network connection for the file to be opened locally without delay. Is there a way to force the client to open the locally cached copy first (without having to unplug the cable), or configure NT4.0 server to do automatic caching (like Win2000 server is capable of).