I had the same problem. I had 18.5.1 installed and just wanted to update but couldn't get through and had the black screen problem.
So i thought maybe clean installing straight to 18.7.1 would make it work but to no avail.
Saw someone suggested to install 18.2.1 first then try updating it to the latest driver. I clean installed the 18.2.1 driver and it worked for me.
I would suggest you to do the same thing.
188.8.131.52 was the last good Driver from ATI coug* AMD and after that they went downhill!!!!!!!!!! AMD Driver are worsted than rotten Meat...…….