What would you expect? most games aren't for mac. Unless you install a windows operating system on it.
I guess that if you're on an iMac, there's nearly not enough power in it to run the game, even when dual booting Windows on it. Macs have a tendency to be more of an furnituring accessory than a gaming machine.
ON-TOPIC: Please quit. Just get Parallels. OFF-TOPIC: Guy above me, where do get those nifty banners? I have always wanted one.
Did they tell you how? I'm also interested in one. On-topic- Wasn't it mentioned sometime in the past that it probably wouldn't be released for mac at least in its first stages?