The intereting thing with this is that I am having the same problem and am also using the latest version of ATI graphics cards drivers.
Looking at the spore thread here it would appear the advice then was to roll back from the 9.- series to the 8.12 update. Saying there seemed to be an issue with this new set of drivers.
Unfortunately I can no longer get 8.12
I am just wondering if this might be more an ATI issue. Another thing I noticed is this only started happening to me when I had 4 controllable sims in one house, which also happens to be the time they moved out of Maxis houses into downloaded ones.
I remember the old problems that we used to have with Nvadia cards with TS2 and in a way this feels similar. The same kind of thing is happening each time. It is after I have a bigger family, it came up after an age transition and is not going away after that.
Another factor with this is I have had this game since the 5th and this only really happened yesterday. I have played for hours at a time to no ill effect now all of a sudden Save Error Code 13 rears its head and now my game does that all the time and crashes!
I have even reduced the quality of my graphics to no avail.