Whenever I try to shutdown/restart from the system tab, I am given the option to log out or lock and pressing them does nothing. shutting down from the terminal works fine using commands like shutdown -h and I can shut down through steam big picture.
This problem just turned up out from the blue just a few days ago and I have been looking for a fix, but I have just be going round in cycles.
Help will be appreciated!
Probably it is dconf issue that you have just described. On your terminal window (ctrl+alt+T) and type this:
dconf reset -f "/home/yourusername/"
note: must use / in the end of the path
dconf is what holds all of the values and defaults factors for Unity thus, that's what controls the reboot/shutdown buttons. This function reset all of dcnof and bring default back. It'd might do the trick in your situation.
