Re: Gnome hangs on 'quit' button
Sometimes a background application is still mananaging something and need time to be closed.
Other times applications in other workspaces are in a popup menu (something like : the file has not been saved, do you want to save ?) and those pop up block the shutdown procedure. Usually the mouse will not work in changing workspaces, but you can use ctrl-alt+arrow keys to reach the popup and close it.
Try also to launch shutdown from terminal with '-h now' options and see what happens.
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