Can’t connect to server!

I have two clients (WinME and Win2K) that can’t connect to our server (WinNT4) I am using static IP addressing, three cascaded SMC switches, and all configurations are correct (i.e. subnet masking, etc…) If I reboot the server, I can get connectivity, but after time has passes, it is lost. I have recieved errror SNMPCantGetEntryPointForEnterpriseOID and tracked it down to my HP Jetdirect print server. I have since reinstalled both printers attached, and the admin program for said print server, as well as reapplied SP6. SNMP is no longer installed. Any other ideas…?