Hi,
This may be by design or there may be a reason for it which I don't know.
In the x86_64 repository for CentOS 6.4, the i686 version of these packages below are not up to date. This causes yum to complain about 'Protected multilib versions'.
* iscsi-initiator-utils-6.2.0.873-2.el6 * iscsi-initiator-utils-devel-6.2.0.873-2 * control-center-filesystem-2.28.1-38
There may be others but these are the three I had to fix manually on my system.
I just downloaded the i686 versions from the i386 repository which seem to work fine.
John.