Local Gigabyte assistance Center? In Florence I think, not too far from here.
Shop is not local. I'm in Siena, shop is in Latina (close to Rome), it's a very reknowed and important online shop in my country.
From this point of view I'm glad that in the end, after a full week of throrough and stressing tests, I was able to identify the problem in my system (i.e. the videocard), otherwise I would have had to send them my WHOLE system, and that would have been a mess, and expensive.
I already did some tests with 3 different PCs with my GTX 670 Windforce. In my new PC, my old PC, and a friend's PC who has a very very similar configuration to mine (same processor, different motherboard but same chipset) and we switched videocards.
His card worked fine on my system, mine produced the same errors on his system.
That's how I've been able to isolate the problem, because as you probably have already read, this problem appears only in PCIE 3.0 16x, the videocard works fine in, like, PCIE 2.0, and that's why when I tried it on my old PC I couldn't spot any issue.
Also, it is not a general issue of ALL GTX 670 Windforce. I have friends who bought a system IDENTICAL to mine on the same shop, and their card works just fine. But this is pretty obvious anyway, if this was a matter of ALL cards, you would have seen THOUSANDS of posts over these boards, and not just a few.
Last but not least, it seems this might be an incompatibility between SOME "print" of the Gigabyte GTX 670 Windforce and SOME PCIE 3.0 chipset. Like the X79 and the Z77 for instance, since appearently it works just fine on Z68.
All in all, I'll never stop to say how STRANGE this issue is. I've been a technical PC assistant for more than 15 years and I swear I've never seen an issue as strange as this one.