Comment 9 for bug 423252

Had the same problem, installing nscd seems to have solved the issue.

However, I noticed that I had that issue with ldap users, when I was accessing ldap over SSL:

my nsswitch.conf (only usefull lines...):
----------------------------------------
passwd: files ldap [NOTFOUND=return] db
group: files ldap [NOTFOUND=return] db
shadow: files
---------------------------------------

my /etc/ldap.conf :
-----------------------------------------
base ********************
host ********************
ldap_version 3

ssl on
tls_cacertfile /etc/ssl/certs/myCA.crt
tls_checkpeer on

pam_password_prohibit_message Please use Wiki to change your password

bind_policy soft
nss_initgroups_ignoreusers avahi,avahi-autoipd,backup,bin,clamav,couchdb,daemon,dhcpd,freerad,games,gdm,gnats,haldaemon,hplip,irc,kernoops,klog,libuuid,list,lp,mail,man,mcn,messagebus,michael,mysql,news,ntp,ntpd,openldap,pdns,polkituser,postfix,proxy,pulse,root,saned,sftp,snmp,speech-dispatcher,sshd,sync,sys,syslog,uml-net,uucp,vde2-net,www-data
-----------------------------------------

Just changing ssl from 'off' to 'on' made me have the issue.... and reverting it back to 'off' made it work again....

Hope this helps