yp weirdness

[Hannu Visti]

I have a 4d/25 running irix 3.3.1. The machine worked fine until I made
it a yp-client. The server is a sun 4 running sunos 4.0.3.
If I use the iris as "local" user (root, guest), everything works, but
if I the account is from yp, absolutely nothing works, most of the
programs dump core (su, rlogin, id, for example.) ypcat shows correctly
the yellow pages password file. 
Any ideas? When I started the client, I turned yp on and set the domainname.
Should I do also something else?