WHY?

OK… I have a Windows 98 SE workstation that I have several drives mapped to a Windows 2000 machine and one to a 95 machine. I can access the drive on the Win 95 machine fine, but the drives on the Win2K machine I can’t access after a while. I haveto totally reboot the 98 Work Station after it locks up when trying to access the 2K drives. Any ideas? Thanks!