Multi screen crash

[greg]

I'm trying to test the Amnesia demo through Steam.

When I start the game, I have a black screen. After a while, if I'm lucky, I have the game menu. I can even start a game, but it crashes rapidly. Total hang of the computer, reboot needed.

I *think* the crash occurs when the mouse moves out of the game screen.

I'm using Ubuntu 12.10 with multiple screen (NOT dual head, therefore xinerama on) with 2 nvidia cards (driver version 304.51).

Any idea??

TIA

greg