I just installed an AMD Radeon HD 5450 card in my computer with DVI, HDMI and VGA ports. I connected my 28" Hanns.G iF281 monitor to the HDMI and my small Dell monitor to the DVI. When hooked to an Radeon HD 5450 the monitor will never enter sleep mode. It doesn't matter if my other monitors had turned off due to an idle timeout or if the computer was off, the Hanns.G iF281 will just stay on and display a cable disconnected message. I have used this monitor with several other computers over the years without this issue, so I know it's specific to this graphics card change. I see that someone had the same issue with Nvidia and came up with a registry fix, but I can't find any fix for my Radeon. If I can't fix this, I will have to return the card and get an Nvidia. Below is the link to the fix that someone else made. Thanks!