Problem with Netatalk, user timeout seems to take down whole network
 

I've got a Mandrake 8.1 server here running netatalk, as well as samba, internet routing, named, and a few others.
We had a problem where Samba related portscans would take down the network, but we dealt with that.
Now, looking at the logs, it seems that there is a problem with netatalk. I'm not sure what version we have, but it's fairly recent.
The logs indicate that precisely at the time the network goes down, a certain user account has just timed out, so I suspect it has something to do with netatalk.
Is this a known problem? Is there any way I can isolate netatalk so that at least it doesn't take down the rest of our services?
Thanks