Hi,
this is just a small glitch but it should be simple to fix...
The game screen auto scrolls whenever the mouse cursor approaches the respective screen border. Well, this is not true in multi-monitor set-ups where the screen is extended over two monitors. Here, it does not auto-scroll on the edge where the other monitor is virtually attached, because the game does not "see it" as an edge of the screen - yet is is, the game does not run on the extended monitor.
It is still possible to scroll with the arrow keys (or kill the other monitor) but this should not be hard to fix...
Dan