cpanのurllistがどうこうのエラー

cpanで突然パッケージをインストールできなくなる。

cpan[1]> install IMAP::Client
CPAN: Storable loaded ok (v2.16)
Going to read '/root/.cpan/Metadata'
  Database was generated on Mon, 12 Jul 2010 18:27:01 GMT
CPAN: Time::HiRes loaded ok (v1.86)
Warning: no success downloading '/root/.cpan/sources/authors/01mailrc.txt.gz.tmp9816'. Giving up on it. at /usr/lib64/perl5/5.8.8/CPAN/FTP.pm line 837

Client not fully configured, please proceed with configuring.

You have not configured a urllist and do not allow connections to the
internet to get a list of mirrors.  If you wish to get a list of CPAN
mirrors to pick from, use this command

    o conf init connect_to_internet_ok urllist

If you do not wish to get a list of mirrors and would prefer to set
your urllist manually, use just this command instead

    o conf init urllist

で、CPAN Sites - www.cpan.orgを見て

cpan> o conf urllist http://ftp.nara.wide.ad.jp/pub/CPAN/
cpan> o conf commit

と設定してもうまくいかなかったけど

cpan> o conf urllist ftp://ftp.nara.wide.ad.jp/pub/CPAN/
cpan> o conf commit

とftp経由にしたらなんか動くようになって、でも結局何が原因だったのかわからずもやもやしている。