2012 MacBook pro freezes

I broke my old 13" MacBook from mid 2008, so I figuredmitmwas time for an upgrade. I purchased a new release 2012 MacBook pro 15" base model since I won't be touching 500gig of data, the quad core 2.3ghz processor should be faster than anything I could need and I would be upgrading to 16gig of ram ASAP. Well, I got it home to realize the ram I bought at micro center was 1333mhz and not 1600mhz as was recommended for the new pros so I left it alone. I downloaded Civilization 5 and started playing with just 4gb ram and it kept freezing quick, so I swapped the ram for the 1333mhz stuff thinking it wouldn't make to much of a difference but that made the whole thing unstable so out it came (I ordered the correct stuff from OWC but didn't want to wait till monday as it was friday and I wanted to play). I then lowered the video options on civ 5 and it seemed to run ok for about 6 hours or so and then it froze the computer. I didn't play again until the new ram arrived yesterday and started playing with the only change to civ 5 being fog of war was on so I would have white instead of black for where I hadnt been and it froze within minutes. Switched to window mode and got a little more time but 10 minutes tops. I'm running osx 10.7.4 with the 2.3ghz processor and 16gb of ram. It was cool when it froze and when it freezes It locks the whole computer up, have to do a hard reset with the power button. I've ran extensive hardware check and it came back fine. I'm not getting error messages just everything stops. Any thoughts on what this is or how to fix it? I bought the 15" for the supposed better graphics card over the 13", which I regret now since I really have no use for a computer this big if it can't play games. And I was only going to mess around with games not get all serious into it. I'm quite bummed as my old MacBook never froze once in the 4+ years I had it.