To ensure CPAN is installed and updated ok:-

perl -MCPAN -e shell
install MD5
install Bundle::CPAN
reload CPAN
quit

To re-configure settings enter o conf init

To remove the top URL to fetch packages from, and shift all the others up one, enter o conf urllist shift

To commit any configuration changes back permanently, enter o conf commit

For more information visit the CPAN website at www.cpan.org/