Windows 2000 Pro/server problems

I have two machines both with the Windows 2000 Pro OS. I am connected by a LAN line and use TCP/IP. The two machines get dropped from the web a different times. It depends on how long I’m on and how many windows I open. We also have 1 Windows 2000 server box that is used not as a DNS ora DHCP but as a workstaion for GIS students. However, a 98SE box has no problems keeping its connection. Furthermore, we use static ip addressing in this office. I changed the hub but still got the same results. I don’t know what to do.