If the user is logged into an account (usera), and then switches to another account (userb) using the "User switch applet" then logs off that account (userb). the user would then be faced with a dialog box that is asking for the password of usera with the following buttons on the dialog box: 
"Leave Message" "Switch User" "Cancel" "Unlock"

Those buttons do not seem to be responsive to mouse clicks, but they do work if i use the tab+enter combination