Comment 18 for bug 89752

Suggestion: In /etc/init.d/checkfs.sh and /etc/init.d/checkroot.sh, at the beginning of the file, place the command:
ls /proc/acpi/ac_adapter. If it's not there, then that's clearly your problem. The thing to check would be the initrd file. to see if it includes the acpi modules:

gunzip < /boot/initrd.img-2.6.24-rc1 | cpio -t | grep acpi

(Replace initrd-2.6.24-rc1 with the name of the initrd of whatever kernel you're running.)

Finally, check /etc/initramfs-tools/initramfs-tools.conf. What is the settings for the MODULES parameter? I've set my config file to:

#
# MODULES: [ most | netboot | dep | list ]
#
# most - Add all framebuffer, acpi, filesystem, and harddrive drivers.
#
# dep - Try and guess which modules to load.
#
# netboot - Add the base modules, network modules, but skip block devices.
#
# list - Only include modules from the 'additional modules' list
#

MODULES=most

It may be that you have this set to "list" or "dep", and it's not picking up the APCI modules as a result.

The problem is I run bleeding edge kernels because I like to live on the edge (and because I like being able to get 8 hours of battery life out of my computer --- see http://thunk.org/tytso/blog/2007/10/29/tip-o-the-hat-wag-o-the-finger-linux-power-savings-for-laptop-users/#comments
for more details. So I don't see things which are clearly kernel packaging and configuration options issues for default ubuntu kernel users. Those issues are important of course; but I'm not the person to debug them....