idmapd maps valid group to "nobody" and "65534"

[Marten Gajda]

Hello,

in my setup I have an OpenLDAP directory for users and groups and a 
Solaris 10 NFSv4 server to distribute home directories.
Client machine is running an OpenVZ Linux kernel and Gentoo.

My Problem is:
I have a group "benutzer" with gid 10001 which has 59 members.
When I add a 60th member to the group "benutzer" idmapd doesn't map this 
group correctly anymore (on the client):

Jul 24 18:13:56 gaia rpc.idmapd[2999]: Client 0: (group) id "10001" -> 
name "nobody"
Jul 24 18:14:30 gaia rpc.idmapd[2999]: Client 0: (group) name 
"benutzer at creavac" -> id "65534"

Everthing else still is mapped properly (all other groups have less 
members).
After removing the 60th user from "benutzer" idmapd maps correctly again:

Jul 24 18:15:05 gaia rpc.idmapd[2999]: Client 0: (group) id "10001" -> 
name "benutzer at creavac"
Jul 24 18:15:30 gaia rpc.idmapd[2999]: Client 0: (group) name 
"benutzer at creavac" -> id "10001"

"getent group benutzer" always gives the correct member list and the 
server also maps correctly.
Local group name resolution (on the client) seems to work fine too.

My idmap.conf looks like:

[General]

Verbosity = 3
Pipefs-Directory = /var/lib/nfs/rpc_pipefs
Domain = creavac

[Mapping]

Nobody-User = nobody
Nobody-Group = nobody

I don't know if this is a idmapd, OpenLDAP or nsswitch (-configuration) 
issue, but as everything else seems to work fine, I'm starting here to 
search.
Maybe someone can give me a hint.

Thank you

Marten