Hello,
The latest update to sudo (sudo-1.7.2p1-14.el5_8.2) breaks postgresql.
https://bugzilla.redhat.com/show_bug.cgi?id=846631
It might break other services that rely on access to /etc/nsswitch.conf too. Assuming you have a "sudoers" line in /etc/nsswitch.conf that file will be recreated with incorrect file permissions.
After having had issues with selinux permissions on that particular file in two previous updates, this time it's the regular file permissions that will break access to /etc/nsswitch.conf for at least postgresql.
Regards, Leonard.