First of all, whether it seems to be working (not crashing) with minimum 12 threads or not, you really should *not* be using that setting on a dual core system. In fact even on a system with 8 or 16 execution units (you have 2), the sheer overhead from managing upwards of 8 threads significantly hampers additional performance from adding cores. The "sweet spot" seems to be about 4 *real* cores and 4 threads, after which there are diminishing returns. Above all you *never* want to specify more threads than you have CPU cores. My suggestion for your settings would be max 2, min 1, or just set them both to 2.
A lower resolution render will definitely behave differently by the way. So it's not surprising that it may not be reproducing your error. Resolution plays a big role in these kinds of problems, and in increasing memory use.
7 for either GI quality setting is probably overkill for most scenes too, unless you have very fine geometry, subtle lighting interactions, and perhaps if you are trying to simulate an indoor environment or a close-up. Otherwise it's really just going to pump up your render time unnecessarily. And that being the case, it makes me wonder if you're using other high settings semi-arbitrarily. What are your other detail settings?
- Oshyan