Imposter

I actually had a frozen game problem recently as well, and I suspect it might be related. While I wasn't left staring at the hidden movement screen, I think I probably would have been if I hadn't had a soldier watching what was happening. What happened was that I had fired a rocket at an alien and missed, setting the ground around it on fire. When the alien took it's turn, it took a potshot at my armored car before stepping into the flames around it and promptly dying. After this, game sounds continued to play and I could move the mouse, but the game was otherwise unresponsive and I was forced to kill it from the task manager.