Workstations shutting down for no apparent reason (F8)

[Alain Cochard]

Hello.  I am running 40 workstations with 3 kinds of hardware, all
under fedora 8.  From time to time -- about once every 3 days -- one
of the machine (not always the same) shuts itself down.  Otherwise
they are running 24 hours a day every day. 

The excerpt of the /var/log/messages that seems relevant to me is
always similar to the following:

Nov 18 15:12:26 epgs16 acpid: received event "button/power PWRF 00000080 00000001"
Nov 18 15:12:26 epgs16 acpid: notifying client 2271[68:68]
Nov 18 15:12:26 epgs16 acpid: notifying client 2467[0:0]
Nov 18 15:12:26 epgs16 acpid: client has disconnected
Nov 18 15:12:26 epgs16 acpid: notifying client 2467[0:0]
Nov 18 15:12:26 epgs16 acpid: client has disconnected
Nov 18 15:12:26 epgs16 acpid: notifying client 2467[0:0]
Nov 18 15:12:26 epgs16 acpid: executing action "/bin/ps awwux | /bin/grep gnome-power-manager | /bin/grep -qv grep || /sbin/shutdown -h now"
Nov 18 15:12:26 epgs16 shutdown[19479]: shutting down for system halt
Nov 18 15:12:26 epgs16 acpid: action exited with status 0
Nov 18 15:12:26 epgs16 acpid: completed event "button/power PWRF 00000080 00000001"
Nov 18 15:12:27 epgs16 avahi-daemon[2211]: Got SIGTERM, quitting.
Nov 18 15:12:27 epgs16 avahi-daemon[2211]: Leaving mDNS multicast group on interface eth0.IPv4 with address 130.79.9.36.
Nov 18 15:12:28 epgs16 hcid[2040]: Stopping SDP server
Nov 18 15:12:28 epgs16 hcid[2040]: Unregister path: /org/bluez
Nov 18 15:12:28 epgs16 input[2065]: Unregistered manager path
Nov 18 15:12:28 epgs16 input[2065]: Exit
Nov 18 15:12:28 epgs16 hcid[2040]: Shutting down local server
Nov 18 15:12:28 epgs16 hcid[2040]: Exit
Nov 18 15:12:28 epgs16 acpid: exiting
Nov 18 15:12:28 epgs16 kernel: Kernel logging (proc) stopped.
Nov 18 15:12:28 epgs16 kernel: Kernel log daemon terminating.
Nov 18 15:12:29 epgs16 rsyslogd: [origin software="rsyslogd" swVersion="1.19.6" x-pid="1974"] exiting on signal 15.

Thanks in advance for any tip on how to solve this problem.

Alain