samba - Jul 2005 - nmbd intermittently delaying responses to name queries

My PDC Samba nmbd is intermittently delaying responses to name queries.  As
an example, i run:

  nmblookup -U 192.168.75.11 -R "PDC#1C"

from a member server, and the .11 machine will respond.  Repeat this a few
times, and the .11 machine stops reponding.  After a while (and you keep
trying, add "-d 10" to the command-line...) the .11 starts responding
again.
Sometimes with what appears to be a queued up set of responses (ie: the
output of nmblookup shows only 2 requests going to the .11 box, but the .11
box responds 12 times).   If I run a "tcpdump port 137" on the .11
box, I
can see the requests arriving at the box.

Ideas?