[Samba] Command tests work but can't browse the network [REVISED]

[Jonathan Ryshpan]

I am a Samba newbie who has just set up a Samba server running under
Fedora Core 3 and a client running under Win 98.  Any attempt to see the
network from "Network Neighborhood" or from "Windows Explorer" fails
with the error box:
        Unable to browse the network
        .
        The network is not accessible
        For more information ...

Also, when I log in, I get the message:
        No domain server was available to validate your password.  You
        may not be able to gain access to some network resources.
Something isn't running on the server.  What is it?

I have run all the tests in the HOWTO section:
	.../Samba-HOWTO-Collection/diagnosis.html
up to and including the last two:
	C:\WINDOWS>net use x: \\claremont\TMP
on the client, which does, in fact make the device x: on my client
equivalent to /tmp on my server, and
        $ nmblookup -M MYGROUP
        querying MYGROUP on 192.168.255.255
        192.168.1.35 MYGROUP<1d>
on the server, which looks OK.

Nevertheless (to repeat) attempts to browse the network from "Network
Neighborhood" or from "Windows Explorer" all fail.

What's going on?