Computer doesn't switch off with 2.6.8-1.521

["Gansser, Martin" <MGansser inneo de>]

hi,

i have installed the 2.6.8.1 from:
http://people.redhat.com/arjanv/2.5/RPMS.kernel/kernel-2.6.8-1.521.i686.rpm
on my FC2 machine.
If i log out and select shutdown the follwing messages are displayed:

Halting system...
md: stopping all md devices.
Shutdown: hdb
Shutdown: hda
Power down.
acpi_power_off called

nothing more happens, with vanilla 2.6.7 Kernel the machine switch.

any hints ?