CentOS - Jan 2010 - Hibernating a laptop with the power button (Thinkpax X31) under CentOS 5.4

I am having a weird problem trying to get hibernation to work when I
press the power button on my Thinkpad X31 under CentOS 5.4.

I've modified /etc/acpi/events/power.conf to contain:

# ACPID config to power down machine if powerbutton is pressed, but only if
# no gnome-power-manager is running

event=button/power.*
action=/bin/ps awwux | /bin/grep gnome-power-manager | /bin/grep -qv grep ||
/sbin/shutdown -h now

And restarted acpid (sudo /sbin/service acpid restart).

I don't run gnome, so there won't be a gnome-power-manager process
running.

When I press the power button nothing happens (acpid does log that it
ran the above action).

If I run the action line above in a shell (as root), the machine does
hibernate just fine.

What is going on here?

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