Samba and DNS

[rparker at VPR.net]

I have half of a class C assigned to my network (/25 netmask
255.255.255.128) and the reverse (PTR) records must be
maintained on my ISP's side. (no one wants the 'hassle' of
working out a scheme to delegate the in-addr-arpa. to us for
half the block) As it stands I have only asked
them to include the server's PTR so that I can ftp, etc. from
sites if I need patches or whatever.

This works fine as I don't really need to advertise my various
Winx clients to the outside world but I see this error quite a
bit in the log.smb:

[2000/09/07 15:34:52, 1] lib/util_sock.c:client_name(852)
  Gethostbyaddr failed for 209.91.24.193
[2000/09/07 15:44:34, 1] lib/util_sock.c:client_name(852)
  Gethostbyaddr failed for 209.91.24.200
[2000/09/07 15:45:03, 1] lib/util_sock.c:client_name(852)
  Gethostbyaddr failed for 209.91.24.193
[2000/09/07 15:49:11, 1] lib/util_sock.c:client_name(852)
  Gethostbyaddr failed for 209.91.24.200

Now, what I understand is that this is because the reverse lookup is
failing (there are no PTR records for these machines at the ISP by
choice). What I am wondering is if I am suffering any kind of
'performance' hit due to these lookup attempts when connections
are made to samba shares by various machines? 

Is this simply an annoying error log message I can ignore, or
are there other implications to this? I have been vexed with my
entire server slowing down to a crawl, even having 'Network
Busy' messages on clients trying to connect at times when I lose all
connectivity to my ISP (and I assume DNS/named becomes quite unhappy
or something of that nature and is spending a lot of time
trying to get answers from the far end about these machines?) 
This is on a BSDI 4.0.1 system running samba  2.0.4b.

Anyone have any insight - thoughts on this?

Thanks also to all the previous comments - one problematic user
had a 3Com network card which had come preinstalled in her
machine. Because of info in recent postings I tried replacing it with a
Netgear card and moved her to a different hub and the
performance increase was remarkable! And as a happy side
effect, the CFO was so pleased she authorized replacing the
rest of the 5+ year old Kingston hubs - all in all a good day in
network land....

many thanks to the denizens of the sambalist -

Rich Parker
Director of Engineering
Vermont Public Radio