I can confirm that this is a huge problem and happened for me as well on a MacBook Pro 15" after installing feisty herd 5, which worked fine, and installing the updates, after which booting was impossible.
-- 2.6.20-10 regression from 2.6.20-9, Macbook Pro no longer boots https://launchpad.net/bugs/91940 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
