this is a paid for and registered install ? right ?
if so a "stab in the dark"
you installed some third party repo ? like RPMforge ,ATRpms, epel or elrepo
and you did not DID NOT
install and configure
see the CentOS wiki on that
but the FULL instructions ARE in the Red Hat Knowledge base
( search for " yum Priorities" )
but you will HAVE to log in to red hat with the username and pass you set up when you registered your install and bought the license
with that out of the way
fixing a mismatch from some rpm installed from an incompatible repo ( that what the plugin tries to PREVENT from happening to begin with )
can you post the output of this
yum repolist all