>    I've my SOHO router running netbsd. I've NAT configured on the WAN
> interface.  I found that for no. of cases, netbios simply don't work. 

NAT breaks lots of things from the Internet Protocol layer up.  In general,
it's not reasonable to expect a protocol to run over NAT  unless someone
has analyzed the protocol and the implementations of the protocol and
determined that they don't violate any of a fairly large number of
(quite reasonable) assumptions.  
(see http://www.cs.utk.edu/~moore/what-nats-break.html for a list)

This is an inherent characteristic of any NAT implementation.  The only
'bug' is that the problems with NATs are not adequately documented - so 
people blame the app or the protocol for problems caused by the imposition
of NATs.

Keith