Maybe it's due to the graphics settings.

That's right, the game crashes for me too if I set the graphics settings lower than "High." Damn Nival. I converted the image to *.dds using some random utility; I'll try doing it in Photoshop later and test it.

And I'm warning you in advance that there are some visual effects on the map, and I honestly don't know how they will look with lower graphics settings.
upd: I've been messing around with it, and it seems like all the critical things are displayed correctly regardless of the graphics settings.

Thanks for the tip! Please report any bugs (even down to incorrect punctuation) – I'd like to polish the map until it shines.