Background:

• kernel RPMs will not update each other, as normal packages would do - instead they get installed in parallel. In order to prevent them from piling up, old+unused kernels will get removed.
• The bug gets triggered if an old kernel is scheduled for removal, while a kernel module for this version is supposed to be updated.

In the case at hand, a new kernel 2.6.9-67.0.15.EL.cern is available, while at the same time an updated version for "kernel-module-openafs" for an older kernel version is available.

Workaround: Turn off the YUM "installonlyn" plugin to allow the problematic transaction to proceed, then turn it on again:

# sed -i -e 's/enabled=.*/enabled=0/' /etc/yum/pluginconf.d/installonlyn.conf
# yum upgrade -y
# sed -i -e 's/enabled=.*/enabled=1/' /etc/yum/pluginconf.d/installonlyn.conf

Should this not work, you can still manually de-install all old and unused kernels and their respective modules. Identify all kernels and their modules, then remove the obsolete ones via a single transaction:

# rpm -qa kernel-\*
# rpm -e kernel-OLDVERSION kernel-module-openafs-OLDVERSION ...