I am using an Asus P5G41T-M motherboard with Core 2 Duo E5300.
I have tried Ubuntu 12.04 beta 2, the latest daily build of 12.04 and 11.10 (the latest official), both of which act in the following strange way:
When shutting down (using
shutdown -h 0,
halt) they get to a point where the splash screen dots are visible, but nothing more happens and the computer doesn't power off.
shutdown -P 0 works, halt and
shutdown -h do not.
I've tried 10.04.4 LTS and it does behave correctly.
Using the newer releases, I've tried adding
acpi=force to the kernel parameters followed by
update-grub, but that didn't help.