Please see the most recent updates in the "Where did the .com name go?" thread. Posts number 16 and 17.
Whats the heat on your card under stress????
I've got the fan on "auto", since running it on 100% would make my 8800 the loudest component of them all.
I just did that flight again with a fresh FSX, traffic and UTX plus the default AI (forgot to remove the .bgl) and activated UTX night lightning (xP). The sim didn't crash, Ram usage peaked at 68%, but I still got those artifacts.
Maybe an error with the (default) scenery itself?

Got my 8800GTX at 95% fan...any less and it gets unhappy but either way it shouldn't cause an oom error...maybe a ctd.
Well its not a completely fresh FSX if it left a bgl behind..So its still tagged in the regestry??????
80°C.
Have you run Memtest to see if its good?
Overheating gfx shouldn't be causing those particular issues in your system.Under stress, 80°C wouldn't bother me too much (9800gx2 and 4870x2 run hotter). If you want it to run a little cooler you could mount a fan to blow across it. I take out my GFX cards every few months and blow them out with compressed air.
Bjoern thats sounds awefully hot and the symptoms you describe would go along with an over heated failing GPU.