Mac OS X 10.9.2 Crash when computer is used intensively.

So I posted this in the OS X section becasue I think this problem has to do with the Software and not the Hardware. I might be wrong so here is the information about my mac as well.

So basically what happens is whenever I run some big program such as Logic Pro X or a game like CS:GO, after few minutes the screen sudenly turns off and then the computer turns off. After that it automatically starts up and gives me a message similar to this one:

After this however, the computer does not always make it to the desktop. It sometimes "blacks out" the same way as I described above, except at the user login prompt. In this case I try to start up the mac in Safe Mode (Hold Shift on Startup), wait for it to boot, restart computer and then loggin back in Regular Mode without any problems. So this is quite a bummer.

After booting I still can check e-mails, brows online, listen to iTunes, watch You-Tube videos and some basic stuff like that. But I can't do anything intense with it. Another wierd thing that happens is whenever I manage to log back on, all the websites that I was logged on such as Facebook, Youtube, etc., suddenly prompts me to log back again, which normaly does not happen once I turn on my computer. Might be a virus, or some crap like that, I don't know.

So, one of the teorries I had is that the computer overheats causing it to force shutdown, however the fans work fine and I could hear them working. More over, my computer does not seem to overheat that much when this happens. I've seen it heat up more before. Next week I'll try opening it up and cleaning all the dust, back up my computer, reset Mavericks and see how it goes. But before that please give me some suggestions. Thank you guys! Will be very much appreciated.