Win2k server

I got Win2k server with few workstation..

I set a batch file script for mapping drive..
let say net use f: \\mainserver\example /yes and sometimes the map drive theres an red sign X and somtimes disconnected.. why is it not consistent..

i even tried without hub, a cross cable..still the same..why is it so?? Even with clean Win2k server installation w/ Active directory installed properly..

Please help…