As of yesterday in the middle of a game of Starcraft 2, my GTX 670 has gone out on me. Not entirely, just I have green and pink horizontal spotted lines across the screen. Also, my second monitor is no longer functioning with the card. When it happened, my resolution settings were thrown out of whack as well leaving me with huge icons, etc. Everything was working perfectly for about a month up until now. Also, the lines seem to interact with the mouse on screen. Thusfar, the actions I've taken have been to get the latest drivers online and restart and update windows though I'm almost certain it's a hardware problem.
Just wanted to update. Took the PC in to my regular trusted shop and where I bought the card. Had a lifetime warranty on it and they said it's most likely faulty. Thanks Sunius for raising my concern though!