I tried to update MySQL from 5.1 to 5.5 in CentOS 6.2. The following is the process I did:
1. rpm -Uvh http://repo.webtatic.com/yum/centos/5/latest.rpm 2. yu
This blog post helped me upgrade from MySQL 5.5.15 to 5.5.28. That upgrade also had the problem with mysql-libs clashing with mysql55-libs.
mysql-libs
mysql55-libs