Radeon R9 290. I use 3 monitors, two DVI and one HDMI.
When the monitors turn off to save power after predefined period, Windows plays the sound of USB disconnected immediately followed by USB connected, after the monitors turned off.
When I move my mouse to wake the PC, it does the same thing again: USB disconnected, then USB connected sound, before turning on monitors.
When monitors turn on, they all start to flicker for about a second or two, similar to when you change the resolution. The problem is that this causes all open windows and applications to move around on the desktop, making a complete mess of whatever layout I had before.
This seems like an issue with the graphic card or drivers, because this started happening after I replaced the graphic card. With my old graphic card this didn't happen - I had the exact same monitors connected with the exact same cables with my old card, and windows would simply turn off and on monitors without disconnecting them or causing any flickering or problems.