This bug has been copied from bug #818585 and has been proposed to be backported to 5.8 z-stream (EUS).
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. http://rhn.redhat.com/errata/RHSA-2012-1149.html
Technical note added. If any revisions are required, please edit the "Technical Notes" field accordingly. All revisions will be proofread by the Engineering Content Services team. New Contents: The sudo update RHSA-2012:0309 introduced a regression that caused the Security-Enhanced Linux (SELinux) context of the "/etc/nsswitch.conf" file to change during the installation or upgrade of the sudo package. This could cause various services confined by SELinux to no longer be permitted to access the file. In reported cases, this issue prevented PostgreSQL and Postfix from starting.