Comment 22 for bug 235768

I had the same issue in natty. For me, it was solved by not using the xorg.conf (by renaming it) and setting twinview with the program disper and running "disper -c".
(the parameter -c clones the output on both devices)

I comment here (and not in bug #162396) because here solutions were proposed and I'm not so sure about the duplicate status: for me, the mouse didn't jump to the other screen, but simply disappeared.