I've been curious about this problem since I played HL2. It is the only game that makes me ill when I'm playing it. I ended up wearing sunglasses just to play it. My eyes would start to hurt then I would get head aches and nausia. Even when slowly walking the character around. I now of some other games where I would get headaches just by watching someone else play, but when I palyed the same game nothing would happen. No, I was not sitting too close to the monitor.