Depois de atualizar todo o seu sistema, você foi instalar um pacote com o yum e aconteceu o seguinte erro:

"There was a problem importing one of the Python modules required to run yum. The error leading to this problem was:

    No module named cElementTree

Please install a package which provides this module, or verify that the module is installed correctly.

It's possible that the above module doesn't match the current version of Python, which is:
2.4.3 (#1, Sep 21 2011, 20:06:00)
[GCC 4.1.2 20080704 (Red Hat 4.1.2-51)]

If you cannot solve this problem yourself, please go to the yum faq at:
    http://wiki.linux.duke.edu/YumFaq"

Para resolver isso, basta remover um pacote antigo do Python:

# rpm -e python-elementtree-1.2.6-7.el4.rf.i386 --nodeps

E baixar e instalar a versão anterior que estava funcionando:

# wget ftp://ftp.nluug.nl/pub/os/Linux/distr/startcom/AS-5.0.0/os/i386/StartCom/RPMS/python-elementtree-1.2.6-5.i386.rpm
# rpm -ivh python-elementtree-1.2.6-5.i386.rpm