This has happened twice now - once in the tutorial, and once in the game itself. Pressing the full screen button to turn the game into/out of full screen is fine, but manually adjusting the size of the browser window causes my Windows XP machine to blue screen and reset.
Blue-screen indicates either a driver problem or a hardware problem. No bug in Card Hunter alone could cause a blue screen crash. The problem you're seeing is almost certainly due to a graphics driver bug which Card Hunter just happens to be triggering. I reckon the problem will go away if you update your graphics drivers.
Yeah, unfortunately, since we're running in Flash inside your browser, this sort of stuff is likely out of our control. Graphics drivers are your best bet.
