I have spent a few days looking for this answer already, but have been unable to find anything. I trying to use my Macbook Air to remote into a Macbook Pro in a different room. Both are using Lion. When I select the Macbook Pro in my Finder window and select "Share Screen", I instantly get remote control of the remote computer, even if my wife is currently using it. If I select "Switch to Virtual Display", my control continues, but the actual screen of the remote computer goes to a grey login screen. If my wife tries to login at this screen on the remote computer, she clicks on her account name and then gets a spinning wheel. That wheel will spin forever... sometimes it stops spinning, but the mouse still moves as a wheel. I would be very exciting if someone here knows how to fix this... and get back my option when logging in to log in with a different account than the one that is currently being used on the remote computer.