You're right, I tried again on both machines and the preseed commands completed successfully. The problem could've been in apt-cacher or archive.ubuntu.com, not sure.
-- Execution of preseeded command failed on Feisty herd 5 https://launchpad.net/bugs/90503 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
