Problem with XPPro connecting to NT4

I have 10 Win98 and 1 XPPro computer in a workgroup with an NT4 server. All computers including the NT server show in network neighborhood of the Win 98 computers. The XPPro machine shows all the Win 98 computers in Network Neighborhood but the server is not showing up.
I’m not sure which end of the network has the problem. Is it XP or the NT server? What is the problem? Any help greatly appriciated.