I'm afraid Noble may be right. I remember the death throes of my Acer some 2 years ago. Had a lot of artifacts while playing EVE Online. Found out it was because its ventilation was clogged in places by cat fur... I removed it, but not before my graphics card was unable to produce anything more than artifacts.
You could check if the problem occurs in a cooler environment. Even having a normal, household fan blowing in the direction of your laptop (preferably the air intake) could help you diagnose, if the problem appears later, if at all, when the laptop is cooler.
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