Network Drives always show red X

I’m running Windows 2000 Pro SP2 on a Gateway 1.5Ghz thats connected to our TCP/IP network using DHCP and WINS. Login scripts map certain network drives. The drives and data are accessible at all times except in Explorer or My Computer they alwayshave the RED X over them which means they’ve disconnected. I can browse the drives at any time with no problem but the RED Xs remain. Any ideas what’s causing this?