Graphics issue, most likely, as you suspected.
I would make sure your graphics drivers are up-to-date, and NEVER get the drivers from Microsoft Update or anything.
Get the drivers from whoever made your card or the chip manufacturer if you can't identify the make.
Alternatively, you could try:
http://www.omegadrivers.net/Also, make sure you fans are all operating properly....if you don't want to or can't open the case, get some kind of temperature monitoring software like SPEEDFAN:
http://www.almico.com/speedfan.phpIf your temps are OK and you still get the problem, try lowering the graphic levels of the game...
Try all that and give us an update.
~archi