Description of problem:

On a HP Omnibook XE3 after I upgraded from
FC-4 to FC-6. When I selected "logout"-> "Turnoff computer", the system would
hang there after the following messages:

...
Halting system...
md: stopping all md devices
shutdown: hda
system halted
Version-Release number of selected component (if applicable):
FC6 X86 fully upgraded from FC4

How reproducible:

Happens every time after I upgraded from FC4

Steps to Reproduce:
1.select "logout"
2.select Turnoff computer
3.
  
Actual results:
...
Halting system...
md: stopping all md devices
shutdown: hda
system halted

then the system hangs and I have to manually press the power button to shut the
system.

Expected results:

The system should proceed through its shut down process.
Additional info:
I have disabled acpi but it doesn't help. Also I tried to boot the system single
user (3), logged in as root
and executed "poweroff", the same problem. I had to shut the power button to
poweroff.