Athelbert, are you able to share the steps you took to fix this issue?
1. I updated all video drivers.
2. I whitelisted the launcher, and both the standard and directx11 executable files (bg3.exe and bg3_dx11.exe, both in the C:\Program Files (x86)\GOG Galaxy\Games\Baldurs Gate 3\bin folder).
3. I have Bitdefender, so after reading the fix above, I then went to the Bitdefender Advanced Threat Defense section and wrote an exception for all three files.
4. All fixed! Or at least got me into the game this morning before work. I'll play later this evening or tomorrow to test out if the rest of the game plays cleanly or not.
Very grateful to the contributors on this thread and in the forums in general. Between the helpful suggestions and bug reports, I have a good feeling about this community.