Power off button disappeared

Is gnome-power-manager running?
Are you using gdm?

Yes it's runing, and yes again i use gdm ...

correction: power manager is not running, error "This program cannot start until you start the dbus session service.This is usually started automatically in X or gnome startup when you start a new session."

What is the output of:
ps -Af | grep dbus
typed in a terminal window

104 3945 1 0 15:34 ? 00:00:00 /usr/bin/dbus-daemon --system
tepaks 4609 4567 0 15:35 ? 00:00:00 /usr/bin/ssh-agent /usr/bin/dbus-launch --exit-with-session x-session-manager
tepaks 4612 1 0 15:35 ? 00:00:00 /usr/bin/dbus-launch --exit-with-session x-session-manager
tepaks 4613 1 0 15:35 ? 00:00:00 dbus-daemon --fork --print-pid 8 --print-address 6 --session
tepaks 4740 4717 0 15:36 pts/0 00:00:00 grep dbus

Strange. dbus seems to be present.

what version of ubuntu are you using ?

ps -Af | grep gnome-power-manager show nothing ?

The error message you mentionned above happens when you try to launch gnome-power-manager from the command line ?

That confuses me to. I'm using 6.06 LTS the Dapper Drake. Output I mentioned is indeed from the command line. Gnome-power manager shows only monitor and sleep settings. The “ps -Af | grep gnome-power-manager” command output is:
tepaks 4569 1 0 21:53 ? 00:00:00 gnome-power-manager
tepaks 4740 4719 0 21:57 pts/0 00:00:00 grep gnome-power-manage

Most strange of all is that it's disappeared just like that. I suppose it came with one of the updates but which one? It seems like there is no end to trouble with Ubuntu. first had problems with GRUB (solved with LILO) than XORG (solved with manual Modeline entry) now this! What's next? OK I know it's new and buggy and better than Breezy bat most of all it's a real challenge. Oh did i mentioned that I'm newbie to Linux?

I have the same issue. Everything seems to be running fine.

Try this :

sudo sed -i "s/SystemMenu=false/SystemMenu=true/" /etc/X11/gdm/gdm.conf
sudo sed -i "s/SystemMenu=false/SystemMenu=true/" /etc/X11/gdm/gdm.conf-custom

That's it! Be sure the switch "Show Actions menu" is checked in Login Window Preferences in your "System > Administration"

I was having this problem as well. Shutdown button dissapeared. Also being a Linux Newbie, i didn't have a clue how to fix it! The above tip worked though.

Thanks!

Please verify this:
go to Menu: System -> Administration -> Login Window

In the first tab "Local" of "Login Window Preferences", check if "Menu Bar: Show Actions menu" is selected.
If no, check it and close the form. If that was the problem it should appear again.

I have a similar problem: I've made a big dist-upgrade from hoary to feisty. After a lot of messing around, everything seems to be working fine, except that in one of the user logins, all icons except the "lock screen" button icon have disappeared from the shutdown menu. The buttons are still functional and the problem only occurs with this one login, so it's not a big thing, but I'm still curious if it can be solved or if I just have to delete the profile and create a new one. I tried searching for config files that contain the names of the icon files, no success. When searching for a solution with google, several people mentioned that beryl could cause such behaviour, so I removed it with apt-get and --purge (although it wasn't running anyway). Any ideas?