I recently upgraded to Windows 8. I installed MSI Afterburner to check the performance of my 2 4890 set in crossfire via CCC. For the first week, everything ran fine : when running Guild Wars 2, my gpu usage on both my cards was the same. Now, it seems like my second card has a lower gpu usage. During heavy load, it would be at 99% on both cards and now it is more like 99% / 80%. Needless to say this degrades the fps of the game.