You can try a utility called
WhoCrashed?, an automatic crash dump analyzer. Upon restart, run this utility and see if it tells you it was a graphics system problem or something else entirely.
I tend to agree that your video card may be overheating. You also could be having CPU overheating. I've seen a breakdown of the thermal paste between the CPU and heat sink that necessitated taking apart the computer, removing and replacing the thermal paste. That also was a failure happening only in SH4, not any other game.
But check out WhoCrashed to see if we're barking up the right tree.
