Almost certainly this is a memory management/overrun issue that Larian needs to fix. All the 'fixes' suggested here (PAE/LAA) simply act to ameliorate the symptoms rather than treat the cause by giving the game process access to a larger chunk of memory, therefore delaying the onset of crashes. The fact that these crashes are occurring on save/load leads me to suspect that data from the previous session isn't being flushed properly.
In my case, with a 64-bit OS and 16GB of RAM, I suspect that I am experiencing these crashes with the same frequency as those of you on x86 systems or with less RAM primarily due to the high resolution I'm running the game at (5760x1080), which is requiring a larger working set. I'd be interested to hear if anyone playing on surround or high-res (eg. 4K) systems is also experiencing the same frequency of crashes.