Sometimes after upgrading your RPM packages with YUM there will be new configuration files generated. These files have .rpmnew tacked onto the end and are created this way so they do not overwrite any configuration file changes you have made. You can find all of the .rpmnew files by running the following command from your shell.
find /etc /var -name *.rpmnew
Once you have located these files do a diff on the .rpmnew files and the original configuration files to see what changes there may be.
diff yum.conf yum.conf.rpmnew
Most of the time you will notice there are no changes and the .rpmnew file can just be deleted. If there are changes merge the differences into your configuration file and then remove the .rpmnew file.
More information about yum can be found on the Fedora Project web site.
