Graphical Oddities (Obstructive shadows, light blue cone, streaks)

This has been happening to me occasionally recently. It doesn't happen every time I play, but it's common enough.

http://www.youtube.com/watch?v=RvCNKys3hNY

Video speaks for itself, but a short description:
Shadows act very strangely, getting a lot bigger than they should. There's green streaks coming from oak every so often a couple minutes in. Lastly, there's that big blue cone that appears occasionally, blocking the whole screen.

This has happened in various locations and difficulties, I just happened to record the Oak fight.

I play at 1920x1080, basic shadows, disabled anti-aliasing, tri-linear filtering, post processing enabled, and fullscreen.

Specs:
Operating System: Windows 7 Home Premium 64-bit
Processor: Intel(R) Core(TM) i7 CPU 870 @ 2.93GHz (8 CPUs), ~2.9GHz
Memory: 4096MB RAM
Card name: NVIDIA GeForce GTX 460
Dedicated Memory: 1 GB

Resetting the game fixes it most of the time. As such, I don't really need support with regards to how I can fix it, I just figured some video of the glitch would be good to share to see if we can figure out what's causing it. My apologies if this is already known, I didn't know what to search for and the things I tried came up with nothing related.

Let me know if you need more information.

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Rory wrote:

This could be a hard to diagnose problem we've been chasing for a while, or it could be a graphics card overheat. It's likely the former, but I'd check your card temperatures while you play just in case, as we don't want to damage anything.

Thanks for the report!

I happen to have been actively monitoring my GPU temperatures while playing PoE, and here's what I've found:

In the first act, temperatures rarely exceed around 70 degrees Celsius and can be around 55 degrees in some empty caves. However in act two, specifically the bright forest areas, temperatures climb rapidly and will taper off at around 85 degrees with 85-90% fan speed. I didn't find any relationship between GPU temperature and these graphical glitches, as I've seen them in caves aswell.

Not to shoot down the possibility that the problem is on my end, just relaying the information for your interpretation.

Thanks for your reply.

Edit: While this may be another issue entirely, while playing act 1 my GPU temps were around 85-90 degrees Celsius at the ship graveyard. I play on pretty much minimum settings so it seems a bit abnormal that it'd be running that hot, but I figured I'd say that it doesn't seem like the act has anything to do with the heat. No graphical glitches yet, however, despite the heat.

Additionally, with default fan settings I stood around and idled at 71 degrees, and with the help of a friend we spammed poison arrow and firestorm for a minute or two until the temperatures leveled off at 91 degrees. Again, this could be unrelated to the original issue but it's worth mentioning that poison arrow and firestorm/ball are our main attacks.