Currently Being ModeratedDec 24, 2011 6:21 PM (in response to Adam Davis4)
I'll ask the same question that preference is probably "asking" itself and why it remains grayed out -- "why do you want fast user switching when there is no other user to switch to?" You said you are the only account. Create another account and see if it is still disabled.
Currently Being ModeratedDec 24, 2011 6:20 PM (in response to Adam Davis4)
Are almost all the options in the panel gray, or just that one?
If you have more than one account, and yet almost all of the options are gray, you need to click the padlock at the bottom and unlock the settings. If it's just the one Fast User Switching option...I dunno!
Currently Being ModeratedDec 27, 2011 8:07 PM (in response to X423424X)
I should have mentioned that I had already created a new account. So, there are two accounts on the machine.
This is the only option on the preference pane that is greyed out. Yes, I have clicked the lock and authenticated as an administrator so that I can make changes. The option is still greyed out.
Currently Being ModeratedDec 27, 2011 8:24 PM (in response to Adam Davis4)
What happens if you log in to the other account and try from there?
Currently Being ModeratedDec 27, 2011 8:43 PM (in response to Király)
You could also try this in Terminal to enable FUS, while logged in to an admin account:
sudo defaults write /Library/Preferences/.GlobalPreferences
MultipleSessionEnabled -bool 'YES'
You might need to reboot for it to take effect.
Currently Being ModeratedJan 19, 2013 11:35 PM (in response to Király)
I have the same problem- I have three accounts on this machine.
The option is greyed out. I tried zapping PRAM, and restarts but no joy.
It coincided with a forced shut-down after an HP update installation hung all day on one of the accounts. "turning off may harm your computer"...
Any clues to a fix would be welcome.