Demo not working?

[Dinges]

I was interested in this game so I decided to download the demo to see what kind of game I could expect before buying it. Unfortunately, I can't make the demo work.

I downloaded the demo whitout using steam, but it didn't work. So I downloaded it again (not working) and then decided that downloading Steam might help. I downloaded Steam and the demo, but still the game wasn't working. I downloaded it again, and renamed the folder described in a similar topic. Nothing seems to help to make the game work!
When I start the game (either in Steam or in non-steam), a window pops up with settings and a button that says 'launch game'. However, when I try to launch the game, the screen turns black and white for a second and then I get a message that says that the game aborted itself.

What should I do to make the game work? I would really like to try the demo first before I buy the game. And actually, if the demo doesn't work, I highly doubt that buying the game would change anything.
Oh and in case the info might help: I use Mac OS X 10.5.8 Leopard