Why does nothing happen when I click "Shutdown" from the "shutdown..." dialog?

Solution 1:

you can try experimenting with different kernel options. try one at a time and see if it has any effect

like for example:

acpi = force or acpi = off

to try one out , when grub(with the selection screen of ubuntu-linux kernels, pops up after you have booted your computer,

press the "e" button to edit your current configuration.
to the line that has the words single quiet, add one of the proposed otions above.

this setting is not permanent over reboot so there is no risk of wrecking anything. if this works, and you want to make it permanent its time for a follow up question :)

Solution 2:

You may also track if there's not a program preventing you from shutting down.

For example, I use a messaging client on my pc (QNetSoul, only for my school), and when I click on the shutdown button for the first time, it will only daemonize the program. Then my computer will not shutdown, even if I wait for an hour. But if I try it a second time, it finally kills it and effectively shutdown.

In your situation, does a second click on the shutdown button turns your computer off? Or is it really prevented from shutting down until you do a sudo halt?

Solution 3:

Do a wright click on your session menu bar. Then there is a possibility to add something to this panel. So add the shutdown button who does appears. This always work. I had the same problem and now i use this button.