Intermittant Connectivity Loss

We are running Windows 2000 with service pack 1 on our servers. Occasionally, our network will “hiccup” and we lose connectivity for several seconds. All of our mapped drives of course end up with red X’s through them which indicates that we have gone offline. We have checked the obvious things: tcp/ip config, hardware connections, cabling, etc. Any suggestions as to some things that I can try to resolve the problem?