I am using Ubuntu 11.10 beta 1. The "power cog" (the button at the top right corner of the screen) seems to have disappeared. I am not sure what caused that because it was there when I installed 11.10 beta 1. So I do not quite remember. The main thing is that I suspect the problem is either gnome-session or cairo dock. Can you help me to get that button back? And when on 22nd this month beta 2 gets out and I use apt-get dist-upgrade, will it install that button once again? Thanks for your help. If you cannot help me, just tell me how to logout (not shutdown) using cairo.
It is called a beta for something. This has happened to me as well several times (11.10 beta 1).
You could search on Launchpad if this bug has already been reported (it'd surprise me if it hasn't been reported yet), and if it hasn't been reported yet, you could report it yourself. To logout, reboot, shutdown, ... you can just press the power button of your computer and it will ask you what it should do. The system settings can be reached using the Unity Dash.