This has happened to me often lately, and it's pretty annoying:
I host a game, and I'm waiting for people to join, so I alt+esc out of the game, go check out something in the web browser, talk on AIM, whatever. Then when I click on Demigod on the taskbar to go see if anybody's joined my game, I get a notice that the game has crashed and I have to ctrl+alt+dlt it (task manager).