I've been using a new system for a few weeks now (see quote at the bottom) and used the 12.10 catalyst drivers and Windows 8 Pro 64 bit. It's been perfectly stable and working fine until yesterday when all of a sudden it started failing. Initially when using the pc, even in idle status while browsing etc, little coloured squares (see screenshot from someone else suffering the same problem). These squares would raise in numbers until they pretty much covered the whole screen and then either the drivers would crash and restart, causing the system to work fine again for a while, or the whole pc would crash and needed to reboot. I tried reinstalling the 12.10 drivers, I tried the 12.11 beta 11 drivers, I tried downgrading to the 12.8 drivers. In each of these cases the proper procedure of uninstalls/reboots/driversweepers etc were used. I also tried restoring a Windows state in which the system was still stable from a few days ago. Somehow my system became more stable again either after reinstalling the 12.10 drivers after I tried the 12.11 beta 11 drivers, or after I used the 12.8 drivers. This means that now idle state of my pc is stable (havent had a single crash yet). I tried playing some games which were easy for the video card such as Hotline Miami and Tony Hawk Pro Skater HD which did not crash (however I assume they will crash eventually). When starting Max Payne 3 however the game/videocard crashes the very moment I start loading a game (before this "semi stable"-state it would crash while showing the Rockstar logo etc at the start of the game). Eventually I tried a game which is somewhat inbetween Max Payne 3 and THPS HD loadwise, namely Warhammer 40K Space Marine. While playing this game I noticed a freeze and immediately alt tabbed to check on MSI Afterburner and noticed the clockspeed of the core and memory both dropped to 150 MHz during this freeze. When I alt tabbed back within seconds it not only froze but the squares/artifacts started appearing and luckily I managed to alt tab and quit the game before my whole PC crashed so I could take another look at MSI Afterburner; same thing; drops of the memory and core speed to 150 MHz. Someone suggested its most likely the card which is unable to determine the correct voltage for it's idle and load status. However I havent been able to find any software which lets me either monitor or control the voltage. Can anyone help me?
Forgot to mention: the temperatures during all this were always around 30-50 degrees celsius, so that's not the problem.
