Ubuntu – Close/minimize/maximize button not appearing

May be you should look into the additional drivers that might be required to enable desktop effects. System->Administration->Additional Drivers.

Alos look at this documentation page Restricted Drivers

I got the same problem ""Failed to load session Ubuntu"" when I was trying to login afer uninstall Compiz.

I tried to boot from USB with Live Ubuntu inside and others ways but it doensnt work.

At the end, it comes up with a simple solution.

1. Boot your Ubuntu as normal
2. When you see the log-in screen, try to Ctrl - Alt - F1
3. In my case (ubuntu 12.10), a blank screen appears. dont be panic, try Ctrl - Alt - F2
4. A login console shows up and ask you to login using your id and password.
5. After login. Run these commands. (tested)

sudo apt-get update
sudo apt-get install unity-2d
sudo apt-get install ubuntu-desktop
sudo apt-get install compizconfig-settings-manager
sudo apt-get install compiz-plugins-extra
sudo apt-get update

I got this above list of commands from How can I remove and re-install Unity? but some doesnt work so I mentioned only good-running command in my case. I highly recommend to restart your system before try to login again.

sudo shutdown -r now

Hope it helps you to solve your problem.

Linh