I (wrongly) did not have my local machine name in /etc/hosts, and only had localhost in there. This was not previously a problem as my named resolved the address, but the 6.0 install overwrote the named.conf leaving me without any way to resolve the local host name. The install did not (incorrectly) overwrite any other configuration file that I have found, but was incorrect in this case. Secondly, many of the services that rely on resolution took excessively long to timeout on non-resolution (e.g. SMB seemed to take about 30 minutes)
The rpm for caching-nameserver has the /etc/named.conf tagged as a config file so when an upgrade is performed normal action would be to created an named.conf.rpmsave of the file unless there was no major changes in config file syntax from one version to another. I did a 5.2 install, made some modifications to the named.conf file. I then did an upgrade to 6.0. The named.conf file that I modified was untouched therefore not a problem. To list the files that would normally be replaced with rpmsaves do rpm -qc caching-nameserver Any of those that you modify yourself should either be backup as rpmsaves or untouched.