Thanks
On the server, /etc/hosts lists:
127.0.0.1 localhost.localdomain
10.10.10.10 conrad.localdomain
I added the other machine to /etc/hosts
10.10.10.11 laptop.localdomain
and now ns_hostbyaddr works, but other stuff remains broken: the page after login - register/user-login.tcl doesn't load, for example. I need to poke around some more, obviously...