Server stops Serving

I have a Windows 2000 server with SP 4 that occassionally stops serving. By this I mean that it is inaccessible from the network. You cannot access the shares on the server and when you do try you get the “network path not found” message. You can however, ping the server just fine you just can’t access resources on it. A reboot will take care of the problem but for how long you can never tell. It seems to be happening more frequently now and there is nothing unusual in the Event Logs. Any ideas on where to begin? Any help would be appreciated.

Thanks.