The Unity version we're currently building with is known to leak memory while rendering shadows (aka. all the time), which is totally bonkers.
You can see this yourself by just loading up a scene and stand around for a while. You'll see the memory usage is gradually climbing at a pretty high rate (couple of megabytes every 1-2 seconds). Sometimes the Garbage Collector can dump a small chunk, but not enough to counteract the memory leak.
"So, why are you building with this version of Unity which has a known memory leak?", you say. Well. It's kind of sad, I'm afraid.
The whole Unity 5 update cycle has been full of bugs in almost every aspect of the engine. Multiple times when updating and testing out a recently released patch, we've seen that they have fixed some stuff (which is often very insignificant fixes compared to some of the major bugs in the engine), but the problem is that some of these patches introduce even more bugs, often major ones.
This has, to say the least, been a frustration beyond imagination.
Now, in the version we're currently using, some things were fixed that we needed to have for DFC. But of course this version also introduced the aforementioned shadow rendering memory leak.
So basically, this is the most stable Unity 5.2 patch to date for us, even if it has the memory leak.
There is a recently released patch of Unity where the memory leak has been fixed, but that version also had a regression bug (among others) which re-introduced a bug where realtime lights in a scene will incorrectly be culled by occlusion culling even though they are in plain view. /facepalm
So yeah, we can't use that version either.
Some major - no, MAJOR - bugs that we are still struggling with in the engine we've seen reports of as far back as March of this year, and even they have yet to be fixed.
Anyway, sorry for the digression, but I just wanted to explain why we're building the game with such a bug in the engine.
With regards to your reported issue, boota:
The error at the bottom of the log you attached doesn't seem like the sort of entry one would get from a normal out of memory issue.
I can't say for certain that is has nothing to do with memory, because it might very well be as a lot of weird stuff will happen as an application starts to use a good chunk of memory, nearing the limit.
Also, it seems like at the point of the crash, you've played for quite some time which may mean that the memory leak mentioned has already started to grab a hold of a lot of your available memory, which then lead to the issue causing the crash.
I've seen this kind of issue only a couple of times before, and it seems to be quite a rare one. It might have something to do with creating memory references to materials or such in-game, but there has been no real clarification of this issue since the first occurrence were reported to Unity staff.
You should, however, be able to re-open the game and continue on from your last saved game.
I'm very sorry for the inconvenience, and I hope we'll be able to squash this one for good sometime soon.