I think Mr Crusty was joking to suggest your graphics card is overheating... Or at least I think he should have been...
Nothing suggests your problem is due to graphics card or memory. For a start you have at least 50% more mem than the guy in the thread you link.
I suggest that you make sure you have no software running in the background, and update the game and your drivers.
If that doesn't fix it then reinstall windows, get your drivers set up, install the game and test.
BTW your post is effectively a request for tech support for that game. If you ask questions like that around here then people are likely to start recommending the hardware that excites them.
Could cost you a packet if you listen
