samba - Oct 1998 - problems accessing samba drives over a SLIP modem line

Hi, I have a wierd problem. Our samba server run on AIX and Solaris,
and 1.9.16 or 17 (I think). Everything works fine on our local
network.

When people come in through an Ascend router using SLIP or PPP however
things don't work quite so well.

The wierd thing is that if the connecting machine is a Unix box, and
there are other PC's on the network on the remote side, net view
\\sambaservername lists the shares available just fine.

However, when we try it directly from NT 4.0 SP3, we get "No network
name found". 

So here's what I've checked:
- use dns for WINS resolution is checked
- tcp/ip is working fine (I can ping, telnet, ftp to the box across
the slip link fine)

Is there any documentation on exactly how MSFT protocols are expected
to work in this case? (Is there any clear description of how samba
handles nt domains vs. workgroups -- our remote machines are logging
into the "local" NT domain named the same name as the hostname, and I
don't know if that's causing this problem or not).

Thanks.