Once I've done that, I can keep playing in full-screen and the mouse works and I have no nasty GIANT CURSOR graphics errors (that have plagued a few of my games). Now however, all I have to do is hit the USE button good and solid, and that's good because it's a lot easier to hit. Meaning I would put my mouse on a large book and try to run it up the screen and then -click-click-click- as it came down, hoping to hit that tiny little box because the mouse will work in windowed mode (though I personally had video resolution problems). Now, before, I had to actually HIT the Fullscreen box to uncheck it. Try using the arrow keys to navigate to the Options tab on the Stalker menu. If I move my mouse really fast on the menu screen, I can briefly see it. My steam updated the other day, and Stalker works for me as well as it did before: meaning the mouse is temporarily stuck at the bottom. I have Stalker: Shadow of Chernobyl on Steam. I have an iMac 10.6.4, Nvidia GeForce 7300 GT, 128 vram, 1gb ram