Some older laptops have trouble enabling the acpi mode. A sign is, when it does't turn itself off after shutting down Ubuntu. Another aspect is the missing knowledge about the battery (is there any? is it loaded?).
During boot process appears this message: BIOS age (1999) fails cutoff(2001).
It will disappear when acpi mode is being forced.

In /boot/grub/menu.lst add acpi=force to the kernel directive.

kernel foobar acpi=force

If there are issues with pc cards, following option perhaps solves the trouble: pci=noacpi