Crash logs are mostly useless, but yours makes it pretty clear what the problem is:
Total virtual memory: 4095 Mb
Free virtual memory: 53 Mb
53 MB isn't enough free memory for the game to save properly, hence the Error 12. Something drove up memory use far too high during this play session. How long did you play before trying to save? Did you spend a lot of time in CAS or Build/Buy? What world are you playing in? How long have you played this save, and how many sims are there in the active household? There are many factors that can drive up RAM use.
On the other hand, this may be a one-off situation; the only way to tell is to test. You can monitor the game's memory use in the Task Manager to see if the problem was related to what you were doing in-game, the save itself, or just a fluke. If you load this save again, what is TS3's RAM use after a few in-game minutes? How about after a couple of hours? If the Task Manager is showing memory use in percentages, right-click on the header to switch to absolute amounts.
