Big graphic glitches with the game

Hey.
So i have this issue for a fairly long time, its a very annoying one.
Basically the problem is this:
Every now and then, while just normally playing, all the sudden the game freezes for like 2-3 seconds or so, then comes back with the entire screen completely glitched and full of graphic artifacts, misplaced textures and weird colors, etc.
Now, first thing to comes to mind is the video card overheating.
But, even on this very hot summer thats striking here, my video card (a GF8600GT, btw) doesn't even hit 65c when in full action, probably thanks to a Zalman ZF900 cooler i bought for it, which works at full speed all the time.
Even before i bought that cooler, the game ran smoothly and my card used to operate at around 80c when ingame.
This, along with the fact that it doesnt look like the typical artifacts caused by overheating, but rather like misplaced textures, leads me to believing this is a software problem, but you can never know which is why i post here.
To demonstrate i took some pictures:

What you see here is obvious, thats the small circle that shows the current state of your ping and FPS, drawn all over the wall.

This one is rather new and showed up just about 30mins ago or so, i dont know exactly what is that.

This one is a month old or something, when i was just hanging in kamadan well all the sudden... well, yeah.
Thanks in advance for any suggestions

oh, and i should probably mention i DO NOT run any texmod mod or something, as i know misplaced textures are common with texmod.

You could always delete your .dat, and re-download it. If that fails, i'll leave it up to those more studied up on hard/software malfunction than me. Best of luck!

Could be overheating. Open the case and clean the dust out.

1. could be a corrupted gw.dat file which means you need to delete it and fast way is to do a -image and redownload it

2. check your drivers make sure they are up to date

3. your vid card might be going faulty

4. like post above said open up your pc once in a while dust the damn thing out.

Fresh from Honur Hill, where my monk decided he goes for a more "darker" look...

Yeah.
Anyway, before i touch the .dat file and do something i might very well regret (god knows how much time it's gonna take to re download all the stuff), im all ears for any additional suggestions.
Right now before touching the .dat file i will probably try to put a floor fan directed near the case which will be open, therefore lowering the temps by alot (even if not im optimal ways), and ill check what happens then, this will at least give me a clue wether its a hardware of software problem.
And thanks for all those who replies

That is a .dat corruption. The graphics card would miss texture passing/creation, etc if that was the issue. This is entire texture replacement, which is the fault of the gw.dat file and nothing else.

It could be .dat corruption, but if -image doesn't fix it, then I think it's a video card fault. These type of faults can be caused by overheating or overclocking or just plain bad hardware.

Are you overclocking anything, btw?