Googling, I found this http://www.ubuntuforums.org/showthread.php?t=198453&page=5 . So you're not alone ...
-- Kernel panic - not syncing: IO-APIC + timer doesn't work! https://launchpad.net/bugs/54621 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
