No mac, no submods.
Game loads up perfectly fine and I can go through character selection/creation without a hitch. However as soon as I get into the game I receive a checksum error and when I unpause, it immediately crashes to desktop. What has me stumped is that I'm running the latest versions of both the game and the mod (2.6.3 and 1.3.2, respectively) and am not using any submods but I still receive the checksum warning. I tried going back to 2.6.2 just to check, but still no luck. I've also been playing the Witcher Kings for 2.6.3 and I haven't had any problems with that so far.
Any ideas what it might be? I'm sure I'm overlooking something so I might just do a quick reinstall.
EDIT: Tried reinstalling but it did nothing. Still get the error message and still get an immediate CTD when the game ticks over to the second day.