Graphics card/cpu overheating?

[schaalman]

Core i7, Nvidia gt525m, NO OVERCLOCKING.....

very often, (especially with payware scenery), screen starts going postal with flashing black areas that make flying a hair short of impossible.

Is this overheating or is it one of the many nuances of FSX?

[Slotback]

It can be a sign of overheating, defective hardware, or bad drivers.

[RaptorF22]

Can you tell us what temperature your running the gpu at when this happens?
You can use something like GPU-Z to find that out.