glibc is package that comes from the OS updates repo I believe. That package requires a glibc common package as well. Can you verify which packages are required for glibc by executing the following:
repoquery –requires glibc
then you should get an output of glibc common package needed and thus you can execute a yum info on that package and verify if it is available or installed. If not available, then maybe then the OS repo might be incorrect.
I hope that helps.