For those who are updating to Win 10 1803 and using AMD's latest driver 18.4.1 and having issues mining (especially ETH), I have a workaround. Either use previous drivers or after updating to latest driver, go to Device Manager and disable/enable your GPU. It works wonder for me. Now latest driver 18.4.1 works and it seems it's slightly faster (around 4%) with same wattage for me. Of course that 4% could be just margin of error.