.. from installing some rpms.
here is a solution that worked for me:
cd /var/lib
chown mysql.root mysql
chmod 755 mysql
The above make me think you installed mysql RPM's am I correct? If you use webmail, check that this works properly as many issues in upgrading/altering mysql resulteed in broken webmail.
One tip for the future, describe problems as detailed as possible, saying stuff doesn't work won't give users on this forum not much to work with. It helps when you tell us what you did before, so if you installed RPM's, specify what RPM's, all actions taken and diagnosis you performed.