度々お世話になっております。
Ubuntu10.04LTS-amd64版のユーザーですが、「レポジトリがDL不可」と以下のように警告されます。

Could not download all repository indexes

The repository may no longer be available or could not be contacted because of network problems. If available an older version of the failed index will be used. Otherwise the repository will be ignored. Check your network connection and ensure the repository address in the preferences is correct.

Failed to fetch http://ppa.launchpad.net/fumiaki-daily/ppa/ubuntu/dists/lucid/main/binary-amd64/Packages.gz  404  Not Found
Some index files failed to download, they have been ignored, or old ones used instead.

どのように、復旧できるか方法を教えていただきたくお願いいたします。