Lubuntu 12.04 screen lock kills ssh session

Friends--

Lubuntu 12.04 fresh install. I login from the computer. I then login via ssh from another computer. When the first session screen locks after X minutes, my ssh session is killed or at least locked. When I go back to the physical machine and login, then I can continue my ssh session. How can I shut off this behavior so my ssh session is not interrupted? But I still want the screen saver/lock to work on this machine when I am accessing it remotely.

Thanks!