I bought a radeon HD 7850 and have been using it happily for years. Recently it has started working only intermittently. I have attempted uninstalling and reinstalling the software, disabling and re-enabling the device, restarting the computer. The only thing that works is restarting the computer but the gfx eventually fails. Integrated gfx on the motherboard still works. Furthermore, sometimes I will not see the GFX card show up under display adapters. Sometimes it shows up as seen below with the "!" and does not work. And other times it shows up like a standard graphics card and functions. I am running out of ideas to diagnose this.
There have been no new software, OS, hardware or other changes.