natd[330]: failed to write packet back (Permission denied)

[bsd at perimeter.co.za]

Hi folks. 

natd[330]: failed to write packet back (Permission denied) 

I've started seeing this message in /var/log/messages recently on one 
gateway server, and it is rather frequent, recurring about 4 times every 
minute. 

Obviously I am running ipfw and natd, and my ipfw ruleset does include use 
of some dummynet pipes.  Also, the box in question is still on 4.3-RELEASE, 
so if this is fixable by updating then that's what I'll do. 

Can anyone clue me in on the cause and perhaps a solution? 

Regards,
Patrick.