Tricky issue with GTX570 - help plz

Hi All,

i have GTX570 (asus make) that i purchased about a year ago.

i started having artifact issues a few months after original purchase, i contacted ASUS tech support, they fixed it and send it back to me, no issues for a few months of very casual gaming, then i started experiencing artifacts again, i contacted ASUS and they sent me another card, they said it is refurbished but tested to be working.
not even 2 weeks later i am seeing artifacts again, but this time its worse, when the artifacts show up the system freezes and i have to Ctrl+Alt+Del then kill the game process.


the problem is persistent across multiple games (BF3 Shogun2 Chernobil Anno2070 etc...).

I used Fur-mark to test the new replacement card as soon as i got it and everything checked fine, now if i run Furmark i have a 50% chance that the artifact+ freeze problem would occur.

i am very confused, i don't know if it is just a series of bad cards, or is it something wrong with other pieces of my machine that is destroying the graphic card(s)?

to the best of my knowledge i used a multimeter and tested the electric cables used by the graphic card, they all displayed 12v as expected...

i have
- Corsair 1000W PSU
- i7920
- GYGABYTE MB
- 6G RAM Corsair dominator
- 2x 1000rpm Raptors
- a DVD RW drive
- he usual USB mouse, KB + a few other things attached through USB


any help or insight is much appreciated.

Thanks!