Internet Connection on Win 2K Pro

Have recently installed ICS on 2 x Wink 2000 Professional machines. 1 has 2 NICS – one connected to the cable modem, the other to the internal network via a hub. Problem is, when its installed from scratch, everything works fine – can browse net andlan from all machines. Leave it for a day or two, or disconnect one machine from the LAN, and the whole system falls over – can ping in one direction, not in the other, can’t browse net from internal LAN, etc etc. Am I wasting my time with ICS? Should I buy a hardware device? SHould I go back to shearing sheep?