Hey Mark,
Well I quickly threw the stock 5770 back in my machine just now and confirmed that BIAB does in fact launch, although I really didn't test it much.
Possibly if you have the stock card you could try it temporarily, just for troubleshooting purposes to see if BIAB launches.

Although I'm not really sure if that could be the problem at this point.
My 7970 is basically an RX380, which the same basic architecture as yours, albeit a lower tier card.

I wasn't sure if you were running an Nvidia card (with those web drivers that change every week). crazy

Like I said it was kind of a long shot, but I figured I'd ask.
Sorry I couldn't be of more help, but hopefully the PG folks will be able to come up with something.

- Jay


MacPro 5,1/12 core@3.46GHz -- OS X 10.14.6 -- ATI 7970 -- 32 Gig RAM -- Crucial 500GB OS SSD -- Samsung EVO 1TB Audio/Sample SSD -- BIAB 2023 -- Logic Pro X -- Cubase Elements 11 -- Too many plugins