Alt+Tab is known to crash the game on ATI cards, and the Windows key is effectively an Alt+Tab.
Yep. It's exceptionally annoying that Stardock still has this issue. I say "still", because GC2 has similar problems. If you alt+tab out of the game you're very likely to not make it back. They never did fix it for GC2 in all that time, so I'm not hopeful that they will for Elemental either.
Somehow SD manages to use DirectX differently from every other developer on the planet, because GC2 and Elemental are the ONLY games I've played that seem to have this problem with ATI cards. :/
Overall, going back to GC2, I'm very disappointed with how this has been handled.