Wish I'd used the in-game report thing but the part of my brain that hates doing extra things right now closed the game rather than filing the bug report, and when the other part of my brain caught up to "this is actually an important report to file," now I gotta take extra steps. Ugh.
Anyway I was playing and I reached for the top right of my keyboard -- I'm pretty sure for a screenshot? can't think what else I would be reaching for up there during the game -- and managed to fumble multiple buttons, and the game immediately crashed. I think my screenshot button is either F11 or F12 (I am not awake enough for this) and I hit some button near them. However, I'm on Dvorak keyboard drivers, so while the F-buttons and the numbers are normal, the others aren't in their usual place. The ones next to the F-buttons that aren't numbers are the brackets, and below that the slash/question mark, equal sign/plus sign, backslash/bar. I don't think I reached any farther down the keyboard, but one of those combos did me in. Might also have included the Print Screen button, Backspace, or Delete, since they're all clustered up there. At a guess, I think the combo was F12+Print Screen, F12+one or both of the brackets, some unholy mixture of all three extra buttons, or F11+F12 (possibly including one of the brackets).
Hope you can fix it! I know I hit weird combos when I fumble the keys, and it's bitten me in the butt a few times when a common shortcut is right next to a doom shortcut (e.g. try to save file, wind up closing program), but Dvorak is still fun and I'm not giving it up.
Fumble a key combo near the Steam screenshot button, I think, using a combo that wouldn't typically occur on a QWERTY keyboard, because I'm using a Dvorak keyboard and the keys are slightly rearranged in that area.