dx11 version seems to lock up on my system if I play around with time of day (moving it around from 6:00, to 7:00, to 8:00, back to 7:00, etc. while flying around generally with nose pointed at or near sun).
I have done it a couple of times now.
It doesn't completely lock up -- it continues to run, but with system thrashing and at a frame rate of about 1 frame every 30 seconds or so.
I have Windows 7 and a GeForce 750 Ti card with drivers from last month (relatively new, but not the very latest).