On this URL: http://wiki.centos.org/Repositories it says:

> Note: You should seriously consider using the Priorities (or
> ProtectBase) yum plugin if you are going to use a 3rd Party
> Repository. (The Priorities and ProtectBase plugins both prevent 3rd
> party repos replacing base packages, but Priorities is much more
> flexible and therefore the recommended plugin.)

Consider removing ProtectBase and installing Priorities