[Samba] smbclient not working on Ubuntu 16.04

[Robert Steinmetz AIA]

I have 4 Ubuntu servers at one site. 3 of the computers can browse the 
Windows network and see all of the Windows computers and the Linux 
servers running Samba. They are running 18.04 LTS. I have one16.04 LTS 
32 bit computer with pretty much the same hardware and software . That 
computer cannot browse the Windows network nor connect to smb/cifs 
shares. It also has shares available and all of the other computers can 
access them. The other computers can see it and can connect to it's 
shares as can all of the Windows computers.

I cannot mount cifs shares

testparm runs without error or warnings.

smbtree runs, prompts for a password but returns no results.

Code:
# smbtree
Enter root's password

nmblookup runs but returns no results.

Code:
# nmblookup -W ADMINISTRATION -A 192.168.1.2
Looking up status of 192.168.1.2
No reply from 192.168.1.2

smbclient runs but times out with an error.

Code:
# smbclient -W ADMINISTRATION -U administrator //shylock2/accounting
Enter administrator's password:
Connection to shylock2 failed (Error NT_STATUS_IO_TIMEOUT)
These commands work on all of the other computers.

I have iptables running on this computer to do address translation for 
my block of public ip addresses. I also have port 137 blocked for udp 
and tcp on the public ip addresses, but I don't think that should effect 
the private addresses.

Code:
-A INPUT -s aa.bb.cc.dd/29 -p udp -m udp --dport 137 -j DROP
-A INPUT -s aa.bb.cc.dd/29 -p tcp -m tcp --dport 137 -j DROP
-A OUTPUT -s aa.bb.cc.dd/29 -p tcp -m tcp --dport 137 -j DROP
-A OUTPUT -s aa.bb.cc.dd/29 -p udp -m udp --dport 137 -j DROP

Disabling ufw doesn't solve the problem.

I haven't found anything in the logs to indicate a problem.
-- 
Rob Steinmetz