We were not able to resolve our issue and decided to disable prelink (there seems to be much differing opinions as to whether or not prelink is still required). If you decide to disable prelink then Dag Wieers has instructions on his web site on how to do this:
Hugh, I found out what caused the problem and worked around it.
I remembered a recent posting to the networker mailing list where certain system tools stopped working correctly since the networker libraries were in the library search path; networker is what sets this machine apart from the other CentOS6 machines.
Using trial and error, and file listings for the networker rpms, I narrowed the problem down and was able to avoid it by adding
# cd /etc/prelink.conf.d # cat networker.conf -b /usr/lib/nsr #