GTX 560 Problem

I won this EVGA GTX 560 from a videogame a while back but it seems i'm the unlucky one that has a broken card. In the first 2-3 days i didn't have any problems with the card or anything like that and then the card started acting really weird like i started seen some small artifacts i think in Diablo 3, then i started to get a pink screen with some small white lines randomly while playing World of Tanks... and now i was browsing the web having nothing opened other then the browser and then i started getting the pink screen again that lasted for 5 seconds the it refreshed and it came back to the normal color. I`m starting to think that the memory on the card is broken cos i had similar problems with a AGP Nvidia card and on that one the memory was damaged completely. Any advice's on what to test before i start getting really paranoid? Already did check for artifacts with that ATI TOOL and left it for about 1h and i had no errors so what to do now?

The pink screen is something like this:

http://www.playtool.com/pages/artifacts/screen0032fh.jp...

But the image is clear in the background only the color is pink and the small lines are from the background image. I got a similar error while browsing the web but that was for like 5 seconds and then the screen refreshed