I'm using WHQL 295.73 drivers and I had the exact same issue, turning off monitor sleep seems to have fixed it. Would be great if it can be fixed though so i can use monitor sleep again.

I hate to bump this topic but I'm having a very similar problem. On some occasions, if I try to watch a video (Youtube, MPC-HC, VLC, etc.) and I'm encoding something that's using DGDecNV, I get a black screen and then upon the screen coming back I get a complaint that my Display Driver quite respon...