cjwatson@drescher:~$ find /srv/launchpad.net/ubuntu-archive/ubuntu/ -type d -perm 0777
/srv/launchpad.net/ubuntu-archive/ubuntu/dists/dapper/main/dist-upgrader-all
/srv/launchpad.net/ubuntu-archive/ubuntu/dists/dapper-updates/main/installer-hppa
/srv/launchpad.net/ubuntu-archive/ubuntu/dists/dapper-updates/main/installer-amd64
/srv/launchpad.net/ubuntu-archive/ubuntu/dists/dapper-updates/main/installer-powerpc
/srv/launchpad.net/ubuntu-archive/ubuntu/dists/dapper-updates/main/installer-sparc
/srv/launchpad.net/ubuntu-archive/ubuntu/dists/dapper-updates/main/installer-ia64
/srv/launchpad.net/ubuntu-archive/ubuntu/dists/dapper-updates/main/installer-i386
/srv/launchpad.net/ubuntu-archive/ubuntu/dists/dapper-updates/main/dist-upgrader-all
/srv/launchpad.net/ubuntu-archive/ubuntu/dists/edgy/main/dist-upgrader-all
/srv/launchpad.net/ubuntu-archive/ubuntu/dists/edgy-updates/main/dist-upgrader-all
/srv/launchpad.net/ubuntu-archive/ubuntu/dists/feisty/main/dist-upgrader-all
/srv/launchpad.net/ubuntu-archive/ubuntu/dists/feisty/main/installer-powerpc
/srv/launchpad.net/ubuntu-archive/ubuntu/dists/feisty/main/installer-amd64
/srv/launchpad.net/ubuntu-archive/ubuntu/dists/feisty/main/installer-i386
/srv/launchpad.net/ubuntu-archive/ubuntu/dists/feisty/main/installer-ia64
/srv/launchpad.net/ubuntu-archive/ubuntu/dists/feisty/main/installer-sparc
World-writable directories aren't really a great idea ...
This is probably a duplicate of bug 107068. While the fix for that bug fixes new custom uploads, it wouldn't affect things already in the archive. Given that you didn't find any gutsy files with this problem, it probably just indicates some existing directories that need their permissions fixed.