In CentOS website, there is a warning about using EPEL:
...So, make SURE you are using the Priorities yum plugin if you are using EPEL...
Below are the steps to install and set the correct priorities:
CentOS 5: yum install yum-priorities
CentOS 6: yum install yum-plugin-priorities
make sure the plugin is enabled
Set highest priority for [base] [updates] and [extra] by adding priority=1 at the end of each part.
If you are using virtualmin repo, makesure the priority for the repo is set to 1 as well.