Inactive elements in the Apple menu

If the "Restart", "Shut Down" and "Log Out..." menu items in the Apple menu don't work, the Kiosk mode is probably enabled:

Run OnyX and type your password.

Click the Parameters icon in the Toolbar and select the Login tab.

Uncheck the "Disable the Restart, Shut Down and Log Out commands in the Apple menu" case.

This problem sometimes occurs after updating the System.