[ubuntu] need help with user switching issues

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http://ubuntuforums.org – I'm having some issues trying to switch users in Ubuntu 12.04.1 LTS using Unity. I have an Administrator account and several user acounts, once logged into the Admin account other users can switch to it without having to input the password. is there any way to force passwords on user switching? I don't want to have to log out each time. also "Lock Screen" doesn't work. clicking it does nothing. if I could get either of these to work I would be happy. thank you in advance. (Hardware)