@tanoo971 Okay, that all looks fine. Does the Sims 3's memory use rise steadily in saves where you get an Error 12? It happens with some saves but not others, and in that case the game will have issues once it's running at around 3.3-3.4 GB RAM, since saving causes a memory spike. If the game throws an Error 12 but doesn't crash, you can always check the Task Manager again immediately afterwards.
If the Error 12s happen without the game using too much memory, then it's running out of a different resource. If you haven't already, turn down water and high-detail lots (in the graphics settings) to no more than "mirrors only" and 2, respectively; these two can use excessive resources otherwise.
Another source of Error 12 can be a lot of "high poly" (high-resolution) custom content, which takes more resources to render than normal cc or base game items. If you have a particular save that's throwing the error and you've confirmed that this is not a RAM issue, and lowering the two graphics settings doesn't help, please try running it without any cc at all, which you can do in a(nother) clean user folder if you don't want to mess up your existing one. Since the cc won't be in the clean folder, you can compare performance in the same save with and without the items. If you're still playing in a custom world, you'll of course need to install that into the new folder, and NRaas mods are fine to add as well, but please don't add anything else.