Orcs Must Die!

If your game crashes all the time, and perhaps you have SLI, try (from the steam forum):

Open the nVidia Control Panel and click on "Manage 3D Settings"
Then add orcsmustdie.exe
Scroll down until you find "SLI rendering mode" and set this to 
"Force alternate frame rendering 1" and accept the warning that pops up
Click Apply

(thanks to Chris for this solution)