There was a post about this issue on the MacRumors Forum:
http://forums.macrumors.com/showthread.php?t=858399
The advise they gave there is to use the arrow keys to go to 'options' and then try to hit the 'full screen' button (to turn off 'full screen') and then hit the 'apply' button. This takes a lot of patience.
However, in the windowed mode, the mouse works.
Here's the problem:
In full-screen, the mouse doesn't work on the menus, so I therefore can't load a game.
In windowed mode, I get this screen:
http://farm5.static.flickr.com/4060/4699527471_b62071ca4f_b.jp
For the initial menu! So I can press enter a couple of time, start a new game, and load a game from there. No problem. But that is a messed up opening menu.
My Star Trek Bridge Commander menu has been doing something similar since 9.0.
The gameplay on S.T.A.L.K.E.R. is great (though I kinda feel the mouse is off-center, so I feel a little drunk when I play), but otherwise, it all works great. Definitely not a gold, but I'd give it a silver since it mostly works.