Yes, I read that link. It basically has what I was going to say (I'll still copy/paste my usual spiel below) but without all the tips and explanation. However, virtual box isn't great from what I understand because it acts like Parallels, which divides the system in half (half the RAM/ half the hdd) for the Windows system and the Mac system. A lot more people prefer using Bootcamp with Windows 7 to play the game on Macs. I refuse to do that on principle, but it's still your best bet. Feel free to ask anything and I'll try to answer.
I'm not sure how much troubleshooting you've already tried, but here's some advice:
If you actually want to "play" the game as it's supposed to work, then get a PC or Bootcamp & Windows for your Mac. The game is not natively written for our systems (I have a mid-2009 Macbook Pro). As long as EA uses Cider, a "wrapper" for the game that enables Macs to play Windows games, it's going to crash with memory issues.
Do not follow EA game advisors' advice without taking into account that many times their advice is wrong for Mac users and can harm our systems. Just use common sense when it comes to their "advice."
Here are two good posts from the Sims 3 Mac forum that have a couple of useful "band-aids" to get the game to work temporarily:
-- http://forum.thesims3.com/jforum/posts/list/658546.page
-- http://forum.thesims3.com/jforum/posts/list/611723.page
Best of luck in your battle to play the Sims 3.
edited to add: In either case, your computer should not be overheating though; mine doesn't yet still crashes which is why I'd be concerned with that.