named error messages in log file, how to fix?

[zz at rockstone.com]

Hi, I have a Redhat 7.1 as gateway/dhcp server for my LAN, 
which has bind-9.1.0-10 running as caching only sever,
The RH7.1 box has two NICs, with Ethernet card real internet ip,
and one card private internal ip 192.168.1.254, internal LAN 
(192.168.1.0/24) machines mostly use the RH7.1 box as resolver.   

I got lots of repeated errors in /etc/var/log/messages:

....
Jun 24 15:46:22 luna named[605]: client 192.168.1.61#137:
error sending response: host unreachable
Jun 24 15:46:23 luna named[605]: client 192.168.1.61#137: 
error sending response: host unreachable
Jun 24 15:46:25 luna named[606]: client 192.168.1.61#137: 
error sending response: host unreachable
....
Jun 24 15:53:24 luna named[606]: client 192.168.1.61#137:
error sending response: host unreachable
Jun 24 15:53:25 luna named[606]: client 192.168.1.61#137:
error sending response: host unreachable
....

those messages repeats from time period of every few seconds
or few munites to max approx every 15min. 

192.168.1.61 is a Win98 machine with only TCP/IP,Client for MS
network and file sharing protocal/service installed. 
And I do NOT have Samba running on this RH7.1 linux, nor
have port 137 to 139 open, I don't understand why the linux
machine attempts to talk to the Win98 with Netbios protocol
as indicated using port 137.  
Any suggestions what's likely the problem and how to 
fix it?  thank you.