This may be a bit late, but this is classic indication of overheating, for both CPU's (processor) and GPU's (graphics processor). Do you regularly clean out your laptop with a can of compressed air? If not, you may want to invest in some. When cleaning, be careful not to let the cooling fans spin too aggressively, as this may strain the fan bearings and ruin the cooling fan itself (this usually isn't too much an issue with laptops as the heat sink [metal fins] is generally more exposed than are cooling fans).
Being that you game on this machine, it is best to avoid letting the laptop sit on fabric (such as carpeting, clothing, etc.) as this will hinder the cooling systems ability to move air and hence cool your laptop. If you do not have a convenient flat surface, such as a dining tray, to sit your laptop upon, several outlets sell cooling pads for laptops, some even come with their own cooling fans to increase heat dissipation.
I look forward to hearing if this resolved your problem.
[Edited for typos]
