I want to add something:
While I was compiling 2.0-RC4, I disabled ACPI_DISABLE_ON_POWEROFF option,
and "halt", "reboot" and "poweroff" now working as expected.
Being sure, I re-enabled
options ACPI_DISABLE_ON_POWEROFF
compiled and rebooted with new kernel. "reboot" command failed.
Then, re-disabled
#options ACPI_DISABLE_ON_POWEROFF
compiled new kernel and rebooted. "reboot" command now working.
I think ACPI_DISABLE_ON_POWEROFF option is suspicious.
By the way, what does this option?
If needed, I can send full kernel config file and dmesg output.

Mustafa Dogan
dogan@politics.ankara.edu.tr