user can't ypcat passwd, but root can

Hi group. first posting to here, so I appologise if this is old news.
It looks like I have a permissions problem that is stopping services not
run as root from seeing a correct value of $USER. Two machines,
'client' & 'server', similar setups apart from one has a full
/etc/passwd from which yp makes maps, and the other has only a skeleton.
This problem has run me ragged. I am sure that I have checked out
everything, and now I hope that someone can show me that I haven't.
Sorry for the mass of detail, but I think it is all relevant.

login on the client as a user not in its skeleton /etc/passwd looks like
this...

[I have no name!@client ~]$ whoami
whoami: cannot find username for UID 501

root@client executes 'ypcat passwd' and sees the full map
root@client executed 'ypcat hosts' and seen the full map
root@server executes 'ypcat passwd' and sees the full map
root@server executed 'ypcat hosts' and seen the full map

user@client executes 'ypcat passwd' and sees 'No such map passwd.byname.
Reason: No such map in server's domain'
user@client executed 'ypcat hosts' and seen the full map
user@server executes 'ypcat passwd' and sees 'No such map passwd.byname.
Reason: No such map in server's domain'
user@server executed 'ypcat hosts' and seen the full map

I am running FC4 ypserv 2.13, ypbind 1.17.2. /var/yp/domain has all the
expected maps portmap, rpc.statd, rpc.idmapd, ypserv, ypbind,
rpc.yppasswdd, rpc.rquotad, nfsd, rpc.mountd are reported by ps as running.

On the client executing 'rpcinfo -p server' reports
portmapper tcp & udp port 111
status tcp & udp port 32768
ypserv 2xudp port 883
& 2xtcp port 886
ypbind 2xudp port 893
& 2xtcp port 896
yppasswdd udp port 759
rquotad 2xudp port 737
& 2xtcp port 752
nfs 3xudp & 3xtcp all on port 2049
nlockmgr 3xudp port 32770
3xtcp port 32795
mountd 3xudp port 771
& 3xtcp port 783

On the client executing 'rpcinfo -p' reports
portmapper tcp & udp port 111
status tcp & udp port 32768
ypbind 2xudp port 648
& 2xtcp port 651
nlockmgr 3xudp port 32769
3xtcp port 32795

/etc/nsswitch.conf on server contains ...
passwd: files nis
shadow: files nis
group: files nis
hosts: files nis dns
bootparams: nisplus [NOTFOUND=return] files
ethers: files
netmasks: files
networks: files
protocols: files nis
rpc: files
services: files nis
netgroup: files nis
publickey: nisplus
automount: files nis
aliases: files nisplus

/etc/nsswitch.conf on clinet contains ...
passwd: nis files
shadow: nis files
group: nis files
hosts: files nis dns
bootparams: nisplus [NOTFOUND=return] files
ethers: files
netmasks: files
networks: files
protocols: files nis
rpc: files
services: files nis
netgroup: files nis
publickey: nisplus
automount: files nis
aliases: files nisplus

/var/yp/Makefile contains
NOPUSH=true
MINUID=500
MINGID=500
NFSNOBODYUID=65534
NFSNOBODYGID=65534
MERGE_PASSWD=true
all: passwd group hosts rpc services netid protocols mail (no more)