Try updating chipset and bios and see if that does work.
For me i had instaler hang with outdated chipset and bios on 19.7.1 which was only recoverable by system restore...
Chipset and bios upgrade worked great for me.
The card's BIOS is the most current version of it, I believe the chipset is as well but I'll have to check that when I get home.
I contacted Sapphire and they said it sounds like a hardware issue and that I should send my receipt in for a warranty request. Problem solved, I guess.