Fixing shutdown problem in hardy

For a long time my ubuntu box can't shutdown properly(not sure when this start to happen may be since upgrade to gusty). Shutdown progress bar will stop running, harddrive already stop spinning and hang. I guess it because my kernel option "acpi=off nolapic irqpoll" in /boot/grub/menu.lst without these option shutdown script work perfect. So, why i need that??
I just found the way to fix this from ubuntuforums. This is not new, many guy has this problem and it fixed. To solve this problem [for me]

1.add "apm=power_off" to kernel option.
2.add "apm power_off=1" to /etc/modules

Reboot and try shutdown again this time it work perfect.